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Punjab State Board PSEB 12th Class English Book Solutions English Grammar Determiners Exercise Questions and Answers, Notes.

PSEB 12th Class English Grammar Determiners

A word qualifying a head word is known as a determiner. Words like a, an, the, that, his, her, my and some are determiners. In grammar, a determiner is a word that is used before a noun to select which instance of the noun you are talking about or to identify it. Determiners are fixing words that determine precisely the meaning of the nouns with which they are used. See the table:

अंग्रेज़ी भाषा में कुछ शब्द ऐसे हैं जिन्हें संज्ञाओं से पहले लगाया जाता है। ये शब्द संज्ञाओं को निश्चित व निर्धारित करने के लिए लगाए जाते हैं। इन शब्दों को Determiners कहते हैं। ये सोलह शब्द हैं-
Determiners तानी डाला हित मतिरे सवर उत निठां ? Nouns 3 पग्लिा प्लाष्टिका मांसा चै । प्टिव ਸ਼ਬਦ Nouns ਨੂੰ ਨਿਸਚਿਤ ਤੇ ਨਿਰਧਾਰਿਤ ਕਰਨ ਲਈ ਲਾਏ ਜਾਂਦੇ ਹਨ । ਇਹ ਸੋਲਾਂ ਸ਼ਬਦ ਹਨ-
this, these, that, those, my, your, his, her, its, our, there, some, any, a, an, the.

Articles. Articles ‘a’, ‘an’ or ‘the’ can also be used as Determiners.
Determiners are of various kinds:
1. Demonstratives – this, that, these, those.
2. Possessives – my, our, your, his, her, its, their, Mohan’s, one’s.
3. Determiners of Quantity – much, more, some, any.
4. Articles – a, an, the are also determiners.

1. Demonstrative Determiners – This, that, these, those.

• This house is Gopal’s.
• That clinic is Dr. Raman’s.
• These books will be sent to the library.
• Those flats will be allotted to us.

2. Possessive Determiners.

• My brother is a pilot.
• Our leaders work for their own kith and kin.
• Your performance is very good.
• His room is very dirty.
• Swami’s father forbade Swami to wander in the sun.
• His house is spacious.
• My coat is black in colour.
• Its pocket is torn.

3. Determiners of Quantity (“some” and “any”).
Some has positive and any has negative implications. Questions with negative implications also have “any”. But questions with positive implications take “some”.

• Have you any money ?
• No, I don’t have any.
• Will you take some more milk ?
• Yes, I will.

4. Articles a, an and the are also used as determiners.

• Here was a possibility.
• What is the matter ?
• He did not know the necessary symptoms.
• He wanted to hold the tooth in reserve.

Note : Our readers should note that all textual exercises on the grammatical items prescribed in the syllabus have been solved at the appropriate places in MBD Guide.

Exercise 1

Fill up the blanks with determiners:

1. ………… watch is broken.
2. ………… of the boys will get a prize.
3. I have not ………… time.
4. There are ………… books on the table.
5. Please give me ………… milk.
6. I do not have ………… money these days.
7. Did not she give you ………… biscuits ?
8. ………… girl will top the list this year also.
9. ………… boys will do well.
10. ………… businessmen make a lot of money.
11. Send ………… student to get the stamps.
12. ………… boy of this class can read it.
13. Give me ………… more juice.
14. There are ………… good books in our library.
Answer:
1. This
2. Each
3. much
4. some
5. some
6. any
7. some
8. Some
9. Some
10. Some
11. any
12. Any
13. some
14. some.

Exercise 2

Fill up the blanks with suitable determiners:

1. ………… egg on the table was thrown away.
2. He has not ………… pen to give you.
3. ………… men are not equal.
4. There is ………… sugar in the tin. You may use it.
5. I have told you ………… hundred times not to come here.
6. There are not ………… buses because the drivers have gone on a strike.
7. Would you like to have ………… coffee ?
8. As ………… patients came into the room, he switched on the fan.
9. He has not eaten ………… food since morning.
10. John refused to give his brother ………… more money.
11. Can you see ………… ants moving on the flower ?
12. ………… teacher can tell you that learning English is not an easy job.
13. Is there ………… food left in the plate ?
14. He has not ………… time to spare.
15. Have you had ………… attacks of malaria ?
16. We can expect ………… more mosquitoes after continued falls of rain.
17. I have not read all the books, but I have read …………
18. Not ………… people like being advised by others.
19. Now the school has ………… pupils than ever before.
20. I exhibited ………… brute in me.
Answer:
1. The
2. a
3. All
4. some
5. a
6. any
7. some
8. more
9. any
10. any.
11. some
12. The
13. any
14. much
15. any
16. some
17. some
18 many
19. more
20. the.

Exercise 3

Fill up the blanks with suitable determiners:

1. ………… road leads to Amritsar.
2. ………… infant cannot look after itself.
3. The beggar was grateful for ………… bread Rani gave him.
4. ………… dinner served at the wedding was not delicious.
5. ………… crow and the owl belong to the same family of birds.
6. He bought ………… mangoes.
7. There are not ………… flowers in the garden now.
8. If you have ………… doubts, please ask your teacher.
9. Will you bring ………… fruit for me ?
10. My elder son first went to ………… school when he was four.
11. He was sent to ………… prison for murdering a man.
12. Do you need ………… help again ?
13. I have ………… pen and a pencil.
14. Moscow is ………… capital of Russia.
15. Rohit has a radio and ………… TV.
16. He has read it in ………… magazine or the other.
17. A good quality is called ………… virtue.
18. It is a very bad mistake to use ‘a’ with ………… plural noun.
Answer:
1. This
2. An
3. the
4. The
5. The
6. some
7. any
8. any
9. any
10. the.
11. the
12. a little
13. a
14. the
15. a
16. some
17. a
18. a.

Exercise 4 (Textual)

Fill in the blanks with suitable determiners:

1. I have ………… friends in the city.
2. ………… umbrella is ………… useful thing.
3. ………… a man has died of cholera.
4. ………… children go to school everyday.
5. Did you see ………… elephants in the forest ?
6. She is proud of ………… beauty.
7. ………… plant is dying.
8. ………… the girls are present today.
9. She did not send me ………… reply.
10. ………… man is expected to do his best.
Answer:
1. many
2. An, a
3. Many
4. These
5. any
6. her
7. That
8. All
9. any
10. Every.

Exercise 5

Fill in the blanks with suitable determiners:

1. He has got ………… bread.
2. How ………… milk do you take daily ?
3. ………… knowledge is a dangerous thing.
4. There is ………… sugar in stock.
5. He gave away ………… money he had in charity.
6. He has broken ………… slate that you bought yesterday.
7. ………… the students are present in the class.
8. I do not have ………… spare pen.
9. ………… body must have his own book.
10. ………… houses are newly built.
Answer:
1. some
2. much
3. A little
4. much
5. the little
6. the
7. All
8. any
9. Every
10. These.

Exercise 6

Fill in the blanks with suitable determiners:

1. Keep to ………… left.
2. Where shall I send ………… fare ?
3. I need ………… money.
4. Can you catch ………… butterfly ?
5. How ………… experience have you got ?
6. He is ………… best boy in the class.
7. Kindly show me ………… pens.
8. I did not buy ………… trousers from the market.
9. There are shady trees on ………… side of the road.
10. How ………… ink is there in the bottle ?
Answer:
1. the
2. the
3. some
4. this
5. much
6. the
7. some
8. any
9. either
10. much.

Exercise 7

Fill in the blanks with suitable determiners:

1. He did not make ………… mistakes in his essay.
2. I have lost appetite, so I did not eat ………… bananas.
3. I must sign ………… will.
4. When I think of India, I think of ………… things.
5. ………… of people go without food in India everyday.
6. She said, ………… pen is mightier than the sword.”
7. ………… book you want is not with me.
8. ………… houses were damaged in the cyclone.
9. I shall return this book in ………… days.
10. I had put in ………… hard work.
Answer:
1. any
2. any
3. the
4. many
5. A lot
6. The
7. The
8. Many
9. a few
10. much.

Exercise 8

Fill in the blanks with suitable determiners:

1. It did not hurt ………… a bit.
2. I covered ………… face and wept.
3. I want ………… title of first Admiral.
4. Who is ………… head of your family ?
5. ………… Ganga is a sacred river.
6. How ………… girls are there in your class ?
7. She toiled up ………… hill.
8. It seemed ………… endless time.
9. Always speak ………… truth.
10. I dismissed him ………… some money.
Answer:
1. me
2. my
3. the
4. the
5. The
6. many
7. the
8. an
9. the
10. with.

Exercise 9

Use suitable determiners in the blanks:

1. I saw ………… girls swimming in the pool.
2. I did not see ………… film last week.
3. He failed to answer ………… questions.
4. Do you have ………… difficulty ?
5. Meet me ………… time you like.
6. Will you make ………… tea for me ?
7. He gave me ………… money.
8. Did he give you ………… information ?
9. ………… cheerleaders were dressed in swimming dresses.
10. ………… women can keep a secret.
Answer:
1. some
2. any
3. some
4. any
5. any
6. some
7. some
8. any
9. The
10. Few.

Exercise 10

Use suitable determiners in the blanks:

1. Can you bring me ………… water to drink ?
2. I am in possession of ………… money in my bank.
3. He has ………… enemies.
4. Did you make ………… mistake in the letter ?
5. ………… a lady is present in the hall.
6. ………… ladies are present in the hall.
7. ………… of what you say is trash.
8. Gayatri is a polyglot because she knows ………… languages.
9. I had to face ………… music.
10. This room has ………… doors.
Answer:
1. some
2. little
3. no
4. any
5. Many
6. Many
7. Much
8. many
9. the
10. two.

Exercise 11

Fill in the blanks with suitable determiners:

1. How ………… money do you want ?
2. All ………… books are lying at sixes and sevens.
3. He lost ………… friends he had.
4. There is ………… milk in the jug.
5. I have ………… work to do.
6. ………… people paid homage to the departed leader.
7. ………… grapes are sweet and juicy.
8. He related ………… interesting story.
9. Jaspreet is ………… taller of them both.
10. Both ………… sons are thieves.
Answer:
1. much
2. the
3. the few
4. little
5. much
6. Several
7. These
8. an
9. the
10. his.

Exercise 12

Fill in the blanks with suitable determiners:

1. ………… member of the party was garlanded.
2. Is there ………… news ?
3. ………… father was a famous physician.
4. ………… horse runs very fast.
5. ………… books lie scattered in the room.
6. Please lend me ………… money.
7. She has ………… daughters.
8. Consult your doctor in case of ………… difficulty.
9. ………… girls are still writing the answer.
10. Only ………… persons came to witness the match.
Answer:
1. Every
2. any
3. My
4. That
5. Her
6. some
7. two
8. any
9. Some
10. a few.

Exercise 13

Fill in the blanks with suitable determiners:

1. Do you have ………… doubt in your mind ?
2. God has created ………… universe.
3. I have ………… good books.
4. Ujwal Puri is going out with ………… Chinese girl.
5. I never have ………… luck with the lottery.
6. Have you got ………… money ?
7. How ………… milk do you need ?
8. ………… time has passed now.
9. I have ………… expectations from anyone.
10. ………… list of new books has been released.
11. ………… road leads to Ajnala.
12. Singing is ………… passion.
13. He tore away ………… resignation letter.
14. She threw her arms around ………… baby.
15. She wrote ………… letter quickly.
Answer:
1. any
2. the
3. many
4. a
5. any
6. any
7. much
8. much
9. no
10. a
11. This
12. my
13. his
14. her
15. a.

Exercise 14

Fill in the blanks with suitable determiners:

1. Have you got ………… Pakistani friends ?
2. No, I haven’t got ………… Pakistani friends ?
3. He has ………… riend at all.
4. She has ………… best friend. They spend all their time together.
5. I have hardly ………… money left.
6. Have you got ………… money ?
7. Would you like ………… more orange juice ?
8. He lives ………… where in London. It does not matter to us.
9. I’m not looking for ………… in particular.
10. There are ………… animals in this zoo.
11. Is there ………… message for me ?
Answer:
1. any
2. any
3. no
4. a
5. any
6. some
7. some
8. some
9. anyone
10. many
11. any.

Exercise 15

Fill in the blanks with suitable determiners:

1. Where shall I send ………… packet ?
2. He sat on ………… seat beside his bed.
3. Shobha knows ………… languages.
4. Hassan lost ………… little sympathy the teacher had for him.
5. How ………… money does he need ?
6. ………… the papers were lying on the floor.
7. There was hardly ………… effort by Hassan to overcome his bad habits.
8. We have ………… things to finish before we go.
9. I had to take ………… responsibility.
10. The big hall has ………… windows.
Answer:
1. this
2. the
3. many
4. the
5. the
6. any
7. many
8. many
9. the
10. many

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 8 Comparing Quantities Ex 8.2 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 8 Comparing Quantities Ex 8.2

1. A man got a 10% increase in his salary. If his new salary is ₹ 1,54,000, find his original salary.
Solution:
Let the original salary be ₹ 100.
After 10% increase, the new salary = ₹ (100 + 10)
= ₹ 110
If his new salary is ₹ 110,
then the original salary = ₹ 100
If new salary is ₹ 1,54,000,
then original salary = (\(\frac {100}{110}\) × 1,54,000)
= 100 × 1400
= ₹ 140000
Thus, his original salary was ₹ 1,40,000.

2. On Sunday 845 people went to the Zoo. On Monday only 169 people went. What is the per cent decrease in the people visiting the Zoo on Monday?
Solution:
Number of people went to the zoo on Sunday = 845
Number of people went to the zoo on Monday = 169
∴ Decrease in the number of people visiting the zoo on Monday = (845 – 169) = 676
Percentage decrease = \(\left(\frac{\text { Decrease }}{\text { Original number }} \times 100\right) \%\)
= (\(\frac {676}{845}\) × 100) %
= 80 %
Thus, 80% decrease in the number of people visiting the zoo on Monday.

3. A shopkeeper buys 80 articles for ₹ 2400 and sells them for a profit of 16%. Find the selling price of one article.
Solution:
Cost price of 80 articles = ₹ 2400
∴ Cost price of 1 article = ₹ \(\frac {2400}{80}\) = ₹ 30
Profit = 16%
∴ Profit on 1 article = ₹ \(\left(\frac{16}{100} \times 30\right)\)
= ₹ 4.80
∴ Selling price of 1 article
= Cost price + Profit
= ₹ 30 + ₹ 4.80
= ₹ 34.80
Thus, selling price of one article is ₹ 34.80.

4. The cost of an article was ₹ 15,500. ₹ 450 were spent on its repairs. If it is sold for a profit of 15%, find the selling price of the article.
Solution:
Cost price of an article = ₹ 15,500
Repair charge (overhead charge) = ₹ 450
∴ Total cost price = Cost price of an article + Overhead expenses
= ₹ (15500 + 450) = ₹ 15,950
Profit per cent = 15%
Amount of profit = 15% of ₹ 15,950
= ₹ \(\left(\frac{15}{100} \times 15950\right)\)
= ₹ \(\left(\frac{23925}{10}\right)\)
= ₹ 2392.50
∴ Selling price = Total cost + Profit
= ₹ (15950 + 2392.50)
= ₹ 18342.50
Thus, the selling price of an article is ₹ 18,342.50.

5. A VCR and TV were bought for ₹ 8000 each. The shopkeeper made a loss of 4% on the VCR and a profit of 8% on the TV. Find the gain or loss per cent on the whole transaction.
Solution:
(i) Cost price of a VCR = ₹ 8000,
Loss per cent = 4 %
∴ Loss amount = 4% of cost
= ₹ \(\left(\frac{4}{100} \times 8000\right)\)
= ₹ (4 × 80)
= ₹ 320
∴ Selling price = Cost price – Loss
= ₹ (8000 – 320)
= ₹ 7680

(ii) Cost price of a TV = ₹ 8000
Profit per cent = 8%
∴ Profit amount = 8 % of cost
= ₹ \(\left(\frac{8}{100} \times 8000\right)\)
= ₹ (8 × 80)
= ₹ 640
∴ Selling price = Cost price + Profit
= ₹ (8000 + 640)
= ₹ 8640
Total cost price of a VCR and TV = ₹ (8000 + 8000)
= ₹ 16,000
Total selling price of a VCR and TV = ₹ (7680 + 8640)
= ₹ 16,320
SP > CR
∴ profit = SP – CP
= ₹ (16,320 – 16,000)
= ₹ 320
∴ Profit per cent = \(\left(\frac{\text { Profit }}{\text { Cost price }} \times 100\right) \%\)
= \(\left(\frac{320}{16000} \times 100\right) \%\)
= 2%
Thus, there is 2% profit on the whole transaction.

6. During a sale, a shop offered a discount of 10% on the marked prices of all the items. What would a customer have to pay for a pair of jeans marked at ₹ 1450 and two shirts marked at ₹ 850 each ?
Solution:
MP of a pair of jeans = ₹ 1450
MP of one shirt = ₹ 850
∴ MP of two shirts = ₹ (2 × 850)
= ₹ 1700
∴ Total MP of three items = ₹ (1450 + 1700)
= ₹ 3150
Discount per cent = 10%
∴ Amount of discount = 10% of total cost
= ₹ \(\left(\frac{10}{100} \times 3150\right)\)
= ₹ 315
Bill amount = MP – Discount
= ₹ (3150 – 315)
= ₹ 2835
Thus, customer would have to pay ₹ 2835 for a pair of jeans and two shirts.

7. A milkman sold two of his buffaloes for ₹ 20,000 each. On one he made a gain of 5 % and on the other a loss of 10%. Find his overall gain or loss. (Hint: Find CP of each)
Solution:
Let CP of 1st buffalo be ₹ x
Gain (Profit) per cent = 5%
Amount of profit = 5 % of CP
= ₹ \(\left(\frac{5}{100} \times x\right)\)
= ₹ \(\frac{5 x}{100}\)
∴ SP = CP + Profit
= ₹ \(\left(x+\frac{5 x}{100}\right)\)
= ₹ \(\left(\frac{100 x+5 x}{100}\right)\)
= ₹ \(\frac{105 x}{100}\)
But, SP of a buffalo = ₹ 20,000 (Given)
∴ \(\frac{105 x}{100}\) = ₹ 20,000
∴ x = ₹ \(\left(\frac{20000 \times 100}{105}\right)\)
= ₹ 19047.62

Let the cost price of 2nd buffalo = ₹ y
Loss per cent = 10%
Amount of loss = 10% of CP
= ₹ \(\left(\frac{10}{100} \times y\right)\)
= ₹ \(\frac{10 y}{100}\)
SP = CP – Loss
= ₹ \(\left(y-\frac{10 y}{100}\right)\)
= ₹ \(\left(\frac{100 y-10 y}{100}\right)\)
= ₹ \(\frac{90 y}{100}\)
But SP of a buffalo = ₹ 20,000 (Given)
∴ \(\frac{90 y}{100}\) = ₹ 20,000
∴ y = ₹ \(\left(\frac{20000 \times 100}{90}\right)\)
= ₹ 22222.22

Total CP of both buffaloes = ₹ (x + y)
= ₹ (19047.62 + 22222.22)
= ₹ 41,269.84

Total SP of both buffaloes = ₹ (20000 + 20000)
= ₹ 40,000
∴ SP < CP
Amount of loss = CP – SP
= ₹ (41269.84 – 40000)
= ₹ 1269.84
Thus, there is overall loss of ₹ 1269.84.

8. The price of a TV is ₹ 13,000. The GST charged on it is at the rate of 12%. Find the amount that Vinod will have to pay if he buys it.
Solution:
Price of a TV = ₹ 13,000
GST per cent = 12%
∴ Amount of GST = 12% of price
= ₹ \(\left(\frac{12}{100} \times 13,000\right)\)
= ₹ 1560
∴ Total amount = Price of a TV + GST
= ₹ (13,000 + 1560)
= ₹ 14,560
Thus, Vinod will have to pay ₹ 14,560.

9. Aran bought a pair of skates at a sale where the discount given was 20%. If the amount he pays is ₹ 1600, find the marked price.
Solution:
Let the MP of a pair of skates be ₹ x.
Discount per cent = 20%
∴ Amount of discount = 20% of MP
= ₹ \(\left(\frac{20}{100} \times x\right)\)
= ₹ \(\frac{20 x}{100}\)
∴ Selling price = MP – Discount
= ₹ \(\left(x-\frac{20 x}{100}\right)\)
= ₹ \(\left(\frac{100 x-20 x}{100}\right)\)
= ₹ \(\frac{80 x}{100}\)
= ₹ \(\frac{4}{5} x\)
But, SP of a pair of skates = ₹ 1600 (Given).
∴ \(\frac{4}{5} x\) = 1600
∴ x = ₹ \(\left(\frac{1600 \times 5}{4}\right)\)
∴ x = ₹ 2000
Thus, the marked price of a pair of skates is ₹ 2000.

10. I purchased a hair dryer for ₹ 5400 including 18% GST. Find the price before GST was added.
Solution:
Cost price of hair dryer with GST = ₹ 5400
GST per cent = 18%
Let the price of a hair dryer before GST ) was added be ₹ x.
∴ Amount of GST = 18% of x
= ₹ \(\left(\frac{18}{100} \times x\right)\)
= ₹ \(\frac{18 x}{100}\)
∴ Price after adding GST = ₹ \(\left(x+\frac{18}{100} x\right)\)
= ₹ \(\left(\frac{100 x+18 x}{100}\right)\)
= ₹ \(\frac{118 x}{100}\)
But, price after adding GST = ₹ 5400 (Given)
∴ \(\frac{118 x}{100}\) = 5400
∴ x = ₹ \(\left(\frac{5400 \times 100}{118}\right)\)
= ₹ 4576.27
Thus, the price of a hair dryer before adding GST is ₹ 4576.27.

11. An article was purchased for ₹ 1239 including GST of 18%. Find the price of the article before GST was added.
Solution:
Such type of sums can be done by two methods.
One method:
Let the price of an article before adding GST be ₹ 100.
GST = 18%
∴ price including GST = ₹ (100 + 18)
= ₹ 118
If price including GST is ₹ 118,
then price before adding GST = ₹ 100
∴ if price including GST is ₹ 1239,
then price before adding GST = ₹ \(\left(\frac{1239}{118} \times 100\right)\)
= ₹ 1050
Thus, the price of an article before adding GST was ₹ 1050.

Another method:
Let the price of an article before adding GST be ₹ x.
GST = 18%
Amount of GST = 18% of ₹ x
= ₹ \(\left(\frac{18}{100} \times x\right)\)
= ₹ \(\frac{18 x}{100}\)
Price after adding GST = ₹ \(\left(x+\frac{18 x}{100}\right)\)
= ₹ \(\left(\frac{118 x}{100}\right)\)
But, the price of an article = ₹ 1239 (Given)
∴ \(\frac{118 x}{100}\) = 1239
∴ x = ₹ \(\left(\frac{1239 \times 100}{118}\right)\)
= ₹ 1050
Thus, the price of an article before adding GST was ₹ 1050.

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 9 Algebraic Expressions and Identities InText Questions and Answers.

PSEB 8th Class Maths Solutions Chapter 9 Algebraic Expressions and Identities InText Questions

Try These: [Textbook Page No. 139]

1. Write two terms which are like:

Question (i)
7xy
Solution:
14xy, 21xy

Question (ii)
4mn²
Solution:
8mn² , – 11mn²

Question (iii)
21
Solution:
– 5l, 9l

Try These : [Textbook Page No. 142]

1. Can you think of two more such situations, where we may need to multiply algebraic expressions?
Solution:
1. Aarush purchased x notebooks and y pens. If cost of a notebook and a pen is same ₹ z, what amount has he to pay? → ₹ z (x + y)
2. Shailja wants to spread a carpet in her room having length (l + 5) m and breadth (b – 2) m. Find the area of the carpet. → (l + 5) (b – 2) m²

Try These: [Textbook Page No. 143]

1. Find 4x × 5y × 7z.
Solution:
4x × 5y × 7z = 4 × 5 × 7 × x × y × z
= 140 xyz

2. Find 4x × 5y × 7z. First find (4x × 5y) and multiply it by 7z; or first find (5y × 7z) and multiply it by 4x. Is the result the same? What do you observe? Does the order in which you carry out the multiplication matter?
Solution:
(4x × 5 y) = 4 × 5 × x × y
= 20xy
Now, 20xy × 7z = 20 × 7 × xy × z
= 140xyz … (i)
Also, (5y × 7z) = 5 × 7 × y × z = 35 yz
Now, 35yz × 4x = 35 × 4 × yz × x
= 140xyz … (ii)
Yes, the result is same.
We can conclude that product remains same if we change order of the terms.

3. Complete the table for area of a rectangle with given length and breadth.
Solution:

length	breadth	area
3x	5y	3x × 5y = 15xy
9y	4y2	9y × 4y2 = 36y3
4ab	5bc	4ab × 5be = 20ab2c
2l2m	3lm2	2l2m × 3lm2 = 6l3m3

Try These : [Textbook Page No. 144]

1. Find the product:

Question (i)
2x (3x + 5xy)
Solution:
= (2x × 3x) + (2x × 5xy)
= 6x² + 10x²y

Question (ii)
a² (2ab – 5c)
Solution:
= (a² × 2ab) – (a² × 5c)
= 2a³b – 5a²c

Try These: [Textbook Page No. 145]

1. Find the product: (4p² + 5p + 7) × 3p
Solution:
(4p² + 5p + 7) × 3p
= (4p² × 3p) + (5p × 3p) + (7 × 3p)
= 12p³ + 15p² + 21p

Try These : [Textbook Page No. 149]

1. Put -b in place of b in Identity (I). Do you get Identity (II)?
Solution:
Identity (I): (a + b)² = a² + 2ab + b²
Let us put (- b) instead of b [a + (- b)]²
= a² + 2a (- b) + (- b)²
∴ (a – b)²
= a² – 2ab + b²
Identity (II): (a – b)² = a² – 2ab + b²
Yes, we get Identity (II).

Try These : [Textbook Page No. 149]

1. Verify Identity (IV), for a = 2, b = 3, x = 5.
Solution:
Identity (IV):
(x + a) (x + b) = x² + (a + b) x + ab
Substitute a = 2, b = 3 and x = 5
LHS
= (x + a) (x + b)
= (5 + 2) (5 + 3)
= (7)(8)
= 56

RHS
= x² + (a + b) x + ab
= (5)² + (2 + 3) × 5 + (2 × 3)
= 25 + (5) × 5 + (6)
= 25 + 25 + 6 = 56
∴ LHS = RHS
∴ The given identity is true for the given values.

2. Consider, the special case of Identity (IV) with a = b, what do you get ? Is it related to Identity (I)?
Solution:
When a = b (∴ Take y for both)
(x + a) (x + b) = x² + (a + b) x + ab
Substitute a = y and b = y
(x + y)(x + y) = x² + (y + y)x + (y × y)
= x² + (2y) x + (y × y) = x² + 2xy + y²
∴ Yes, it is the same as Identity ( I).

3. Consider, the special case of Identity (IV) with a = -c and b = -c. What do you get ? Is it related to Identity (II) ?
Solution:
Identity (IV):
(x + a)(x + b) = x² + (a + b) x + ab
Substitute (- c) instead of a and (- c) instead of b,
(x – c) (x – c)
= x² + [(-c) + (-c)]x + [(-c) × (-c)]
= x² + [- 2c] x + (c²)
= x² – 2cx + c²
∴ Yes, it is the same as Identity (II).

4. Consider the special case of Identity (IV) with b = – a. What do you get ? Is it related to Identity (III)?
Solution :
Identity (IV):
(x + a) (x + b) = x² + (a + b) x + ab
Substitute (-a) instead of b,
(x + a) (x – a)
= x² + [a + (- a)] x + [a × (- a)]
= x² + (a – a) x + [- a²]
= x² + (0) x – a²
= x² – a²
∴ Yes, it is the same as Identity (III).

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 9 Algebraic Expressions and Identities Ex 9.5 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities Ex 9.5

1. Use a suitable identity to get each of the following products:

Question (i)
(x + 3) (x + 3)
Solution:
= (x + 3)²
= (x)² + 2(x)(3) + (3)²
[∵ (a + b)² = a² + 2ab + b²]
= x² + 6x + 9

Question (ii)
(2y + 5) (2y + 5)
Solution:
= (2y + 5)²
= (2y)² + 2 (2y)(5) + (5)²
[∵ (a – b)² = a² – 2ab + b²]
= 4y² + 20y + 25

Question (iii)
(2a – 7) (2a – 7)
Solution:
= (2a – 7)²
= (2a)² – 2(2a)(7) + (7)²
[∵ (a – b)² = a² – 2ab + b²]
= 4a² – 28a + 49

Question (iv)
(3a – \(\frac {1}{2}\))(3a – \(\frac {1}{2}\))
Solution:
= (3a – \(\frac {1}{2}\))²
= (3a)² – 2(3a)(\(\frac {1}{2}\)) + (\(\frac {1}{2}\))²
[∵ (a – b)² = a² – 2ab + b²]
= 9a² – 3a + \(\frac {1}{4}\)

Question (v)
(1.1m – 0.4) (1.1m + 0.4)
Solution:
= (1.1m)² – (0.4)²
[∵ (a + b) (a – b) = a² – b²]
= 1.21m² – 0.16

Question (vi)
(a² + b²) (-a² + b²)
Solution:
= (b² + a²) (b² – a²)
= (b²)² – (a²)²
[∵ (a + b) (a – b) = a² – b²]
= b⁴ – a⁴

Question (vii)
(6x – 7) (6x + 7)
Solution:
= (6x)² – (7)²
[∵ (a + b) (a – b) = a² – b²]
= 36x² – 49

Question (viii)
(-a + c) (-a + c)
Solution:
= (-a + c)²
= (-a)² + 2 (-a) (c) + (c)²
[∵ (a + b)² = a² + 2ab + b²]
= a² – 2ac + c²

Question (ix)
(\(\frac{x}{2}+\frac{3 y}{4}\))
Solution:
= (\(\frac{x}{2}+\frac{3 y}{4}\))²
= (\(\frac {x}{2}\))² + 2(\(\frac {x}{2}\))(\(\frac {3y}{4}\)) + (\(\frac {3y}{4}\))²
[∵ (a + b)² = a² + 2ab + b²]
= \(\frac{x^{2}}{4}+\frac{3 x y}{4}+\frac{9 y^{2}}{16}\)

Question (x)
(7a – 9b) (7a – 9b)
Solution:
= (7a – 9b)²
= (7a)² – 2(7a)(9b) + (9b)²
[∵ (a – b)² = a² – 2ab + bsup>2]
= 49a² – 126ab + 81b²

2. Use the identity (x + a) (x + b) = x² + (a + b) x + ab to find the following products:

Question (i)
(x + 3) (x + 7)
Solution:
Identity : (x + a) (x + b) = x² + (a + b) x + ab
= (x)² + (3 + 7)x + (3) (7)
= x² + (10) x + 21
= x² + 10x + 21

Question (ii)
(4x + 5) (4x + 1)
Solution:
= (4x)² + (5 + 1) 4x + (5)(1)
= 16x² + (6) 4x + 5
= 16x² + 24x + 5

Question (iii)
(4x – 5) (4x – 1)
Solution:
= (4x)² + (- 5 – 1) 4x + (- 5) (- 1)
= 16x² + (- 6) 4x + 5
= 16x² – 24x + 5

Question (iv)
(4x + 5) (4x- 1)
Solution:
= (4x)² + (5 – 1) 4x + (5) (- 1)
= 16x² + (4) 4x – 5
= 16x² + 16x – 5

Question (v)
(2x + 5y) (2x + 3y)
Solution:
= (2x)² + (5y + 3y) 2x + (5y) (3y)
= 4x² + (8y) 2x + 15y²
= 4x² + 16xy + 15y²

Question (vi)
(2a² + 9) (2a² + 5)
Solution:
= (2a²)² + (9 + 5) 2a² + (9)(5)
= 4a⁴ + (14)2a² + 45
= 4a⁴ + 28a² + 45

Question (vii)
(xyz – 4) (xyz – 2)
Solution:
= (xyz)² + (- 4 – 2) xyz + (- 4)(- 2)
= x²y²z² + (- 6) xyz + 8
= x²y²z² – 6xyz + 8

3. Find the following squares by using the identities:

Question (i)
(b – 7)²
Solution:
= (b)² – 2 (b)(7) + (7)²
[∵ (a – b)² = a² – 2ab + b²]
= b² – 14 b + 49

Question (ii)
(xy + 3z)²
Solution:
= (xy)² + 2 (xy)(3z) + (3z)²
[∵ (a + b)² = a² + 2ab + b²]
= x²y² + 6xyz + 9z²

Question (iii)
(6x² – 5y)²
Solution:
= (6x²)² – 2 (6x²) (5y) + (5y)²
[∵ (a – b)² = a² – 2ab + b²]
= 36x⁴ – 60x²y + 25y²

Question (iv)
(\(\frac {2}{3}\)m + \(\frac {3}{2}\)n)²
Solution:
= (\(\frac {2}{3}\)m)² + 2(\(\frac {2}{3}\)m)(\(\frac {3}{2}\)n) + (\(\frac {3}{2}\)n)²
[∵ (a + b)² = a² + 2ab + b²]
= \(\frac {4}{9}\)m² + 2mn + \(\frac {9}{4}\)n²

Question (v)
(0.4p – 0.5q)²
Solution:
= (0.4p)² – 2 (0.4p)(0.5q) + (0.5q)²
[∵ (a – b)² = a² – 2ab + b²]
= 0.16p² – 0.4pq + 0.25q²

Question (vi)
(2xy + 5y)²
Solution:
= (2xy)² + 2 (2xy)(5y) + (5y)²
[∵ (a + b)² = a² + 2ab + b²]
= 4x²y² + 20xy² + 25 y²

4. Simplify:

Question (i)
(a² – b²)²
Solution:
= (a²)² – 2(a²)(b²) + (b²)²
= a⁴ – 2a²b² + b⁴

Question (ii)
(2x + 5)² – (2x – 5)²
Solution:
= [(2x)² + 2(2x)(5) + (5)²] – [(2x)² – 2 (2x)(5) + (5)²]
= [4x² + 20x + 25] – [4x² – 20x + 25]
= 4x² + 20x + 25 – 4x² + 20x – 25
= 4x² – 4x² + 20x + 20x + 25 – 25
= 40x

Question (iii)
(7m – 8n)² + (7m + 8n)²
Solution:
= [(7m)² – 2(7m)(8n) + (8n)²] + [(7m)² + 2 (7m)(8n) + (8n)²]
= [49m² – 112mn + 64n²] + [49m² + 112mn + 64n²]
= 49m² – 112mn + 64n² + 49m² + 112mn + 64n²
= 49m² + 49m² – 112mn + 112mn + 64n² + 64n²
= 98m² + 128n²

Question (iv)
(4m + 5n)² + (5m + 4n)²
Solution:
= [(4m)² + 2 (4m)(5n) + (5n)²] + [(5m)² + 2 (5m)(4n) + (4n)²]
= 16m² + 40mn + 25n² + 25m² + 40mn + 16n²
= 16m² + 25m² + 40mn + 40 mn + 25n² + 16n²
= 41m² + 80mn + 41n²

Question (v)
(2.5p – 1.5q)² – (1.5p – 2.5q)²
Solution:
= [(2.5p)² – 2 (2.5p)(1.5q) + (1.5q)²] – [(1.5p)² – 2 (1.5p)(2.5q) + (2.5q)²]
= [6.25p² – 7.5pq + 2.25q²] – [2.25p² – 7.5pq + 6.25q²]
= 6.25p² – 7.5pq + 2.25q² – 2.25p² + 7.5pq – 6.25q²
= 6.25p² – 2.25p² – 7.5pq + 7.5pq + 2.25q² – 6.25q²
= 4p² – 4q²

Question (vi)
(ab + bc)² – 2ab²c
Solution:
= [(ab)² + 2 (ab)(bc) + (bc)²] – 2ab²c
= a²b² + 2ab²c + b²c² – 2ab²c
= a²b² + 2ab²c – 2ab²c + b²c²
= a²b² + b²c²

Question (vii)
(m² – n²m)² + 2m³n²
Solution:
= [(m²)² – 2 (m²)(n²m)² + (n²m)²] + 2m³n²
= m⁴ – 2 m³n² + n⁴m² + 2 m³ n²
= m⁴ – 2 m³n² + 2 m³n² + n⁴m²
= m⁴ + m²n⁴

5. Show that:

Question (i)
(3x + 7)² – 84x = (3x – 7)²
Solution:
LHS = (3x + 7)² – 84x
= (3x)² + 2(3x)(7) + (7)² – 84x
= 9x² + 42x + 49 – 84x
= 9x² + 42x – 84x + 49
= 9x² – 42x + 49

RHS = (3x – 7)²
= (3x)² – 2(3x)(7) + (7)²
= 9x² – 42x + 49
Thus, LHS = RHS
∴ (3x + 7)² – 84x = (3x – 7)²

Question (ii)
(9p – 5q)² + 180pq = (9p + 5q)²
Solution:
LHS = (9p – 5q)² + 180pq
= (9p)² – 2(9p)(5q) + (5q)² + 180pq
= 81p² – 90pq + 25q² + 180pq
= 81p² – 90pq + 180pq + 25q²
= 81p² + 90pq + 25q²

RHS = (9p + 5q)²
= (9p)² + 2(9p)(5q) + (5q)²
= 81p² + 90pq + 25q²
Thus, LHS = RHS
∴ (9p – 5q)² + 180pq = (9p + 5q)²

Question (iii)
(\(\frac {4}{3}\)m – \(\frac {3}{4}\)n)² + 2mn = \(\frac {16}{9}\)m² + \(\frac {9}{16}\)n²
Solution:
LHS = [\(\frac {4}{3}\)m – \(\frac {3}{4}\)n]² + 2mn
= [(\(\frac {4}{3}\)m)² – 2(\(\frac {4}{3}\)m)(\(\frac {3}{4}\)n) + (\(\frac {3}{4}\)n)²] + 2mn
= \(\frac {16}{9}\)m² – 2mn + \(\frac {9}{16}\)n² + 2mn
= \(\frac {16}{9}\)m² – 2mn + 2mn + \(\frac {9}{16}\)n²
= \(\frac {16}{9}\)m² + \(\frac {9}{16}\)n² = RHS
Thus, LHS = RHS
∴ (\(\frac {4}{3}\)m – \(\frac {3}{4}\)n)² + 2mn = \(\frac {16}{9}\)m² + \(\frac {9}{16}\)n²

Question (iv)
(4pq + 3q)² – (4pq – 3q)² = 48pq²
Solution:
LHS = (4pq + 3q)² – (4pq – 3q)²
= [(4pq)² + 2 (4pq)(3q) + (3q)²] – [(4pq)² – 2 (4pq)(3q) + (3q)²]
= [16p²q² + 24pq² + 9q²] – [16p²q² – 24pq² + 9q²]
= 16p²q² + 24pq² + 9q² – 16p²q² + 24pq² – 9q²
= 16p²q² – 16p²q² + 24pq² + 24pq² + 9q² – 9q²
= 48pq² = RHS
Thus, LHS = RHS
∴ (4pq + 3q)² – (4pq – 3q)² = 48pq²

Question (v)
(a – b) (a + b) + (b – c) (b + c) + (c – a) (c + a) = 0
Solution:
LHS = (a – b)(a + b) + (b – c)(b + c) + (c – a) (c + a)
= (a² – b²) + (b² – c²) + (c² – a²)
= a² – b² + b² – c² + c² – a²
= a² – a² + b² – b² + c² – c²
= 0 = RHS
Thus, LHS = RHS
∴ (a -b)(a + b) + (b- c) (b + c) + (c – a) (c + a) = 0

6. Using identities, evaluate:

Question (i)
71²
Solution:
= (70 + 1)²
= (70)² + 2 (70)(1) + (1)²
[∵ (a + b)² = a² + 2ab + b²]
= 4900 + 140 + 1
= 5041

Question (ii)
99²
Solution:
= (100 – 1)2
= (100)² – 2(100)(1) + (1)²
[∵ (a – b)² – a² – 2ab + b²]
= 10000 – 200 + 1
= 9801

Question (iii)
102²
Solution:
= (100 + 2)²
= (100)² + 2 (100)(2) + (2)²
[∵ (a + b)² = a² + 2ab + b²]
= 10000 + 400 + 4
= 10404

Question (iv)
998²
Solution:
= (1000 – 2)²
= (1000)² – 2 (1000)(2) + (2)²
[∵ (a – b)² = a² – 2ab + b²]
= 1000000 – 4000 + 4
= 996004

Question (v)
5.2²
Solution:
= (5 + 0.2)²
= (5)² + 2 (5)(0.2) + (0.2)²
[∵ (a + b)² = a² + 2ab + b²]
= 25 + 2 + 0.04
= 27 + 0.04
= 27.04

Question (vi)
297 × 303
Solution:
= (300 – 3) × (300 + 3)
= (300)² – (3)²
[∵ (a – b)(a + b) = a² – b²]
= 90000 – 9
= 89991

Question (vii)
78 × 82
Solution:
= (80 – 2) × (80 + 2)
= (80)² – (2)²
[∵ (a – b)(a + b) = a² – b²]
= 6400 – 4
= 6396

Question (viii)
8.9²
Solution:
= (9 – 0.1)²
= (9)² – 2(9)(0.1) + (0.1)²
[∵ (a – b)² = a² – 2ab + b²]
= 81 – 1.8 + 0.01
= 81.01 – 1.8
= 79.21

Question (ix)
10.5 × 9.5
Solution:
= (10 + 0.5) × (10 – 0.5)
= (10)² – (0.5)²
[∵ (a + b)(a – b) = a² – b²]
= 100 – 0.25
= 99.75

7. Using a² – b² = (a + b) (a – b), find:

Question (i)
51² – 49²
Solution:
= (51 + 49) (51 – 49)
= (100) × (2)
= 200

Question (ii)
(1.02)² – (0.98)²
Solution:
= (1.02 + 0.98) (1.02 – 0.98)
= (2.0) × (0.04)
= 0.08

Question (iii)
153² – 147²
Solution:
= (153 + 147) (153 – 147)
= (300) × (6)
= 1800

Question (iv)
12.1² – 7.9²
Solution:
= (12.1 + 7.9) (12.1 – 7.9)
= 20 × 4.2
= 84

8. Using (x + a)(x + b) = x² + (a + b) x + ab, find:

Question (i)
103 × 104
Solution:
= (100 + 3) × (100 + 4)
= (100)² + (3 + 4) × 100 + (3)(4)
= 10000 + 700 + 12
=10712

Question (ii)
5.1 × 5.2
Solution:
= (5 + 0.1) (5 + 0.2)
= (5)² + (0.1 + 0.2) × 5 + (0.1)(0.2)
= 25 + (0.3) × 5 + 0.02
= 25 + 1.5 + 0.02
= 26.52

Question (iii)
103 × 98
Solution:
= (100 + 3) (100-2)
= (100)² + (3 – 2) 100 + (3)(-2)
= 10000 + 100 – 6
= 10094

Question (iv)
9.7 × 9.8
Solution:
= (10 – 0.3) (10 – 0.2)
= (10)² + [(-0.3) + (-0.2)] 10 + (-0.3) (-0.2)
= 100 + [-0.5] × 10 + 0.06
= 100 – 5 + 0.06
= 95.06

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 8 Comparing Quantities Ex 8.1 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 8 Comparing Quantities Ex 8.1

1. Find the ratio of the following.

Question (a).
Speed of a cycle 15 km per hour to the speed of scooter 30 km per hour.
Solution:
Speed of a cycle = 15 km/h
Speed of a scooter = 30 km / h
∴ Ratio of the speed of a cycle to the speed of a scooter
= \(\frac{15 \mathrm{~km} / \mathrm{h}}{30 \mathrm{~km} / \mathrm{h}}\)
= \(\frac {1}{2}\)
= 1 : 2

Question (b).
5 m to 10 km
Solution:
[Note : Unit of both quantities should be same.]
1 km = 1000 m
∴ 10 km = 10 × 1000 m
= 10,000 m
∴ Ratio of 5 m to 10 km = \(\frac{5 \mathrm{~m}}{10 \mathrm{~km}}\)
= \(\frac{5 \mathrm{~m}}{10000 \mathrm{~m}}\)
= \(\frac{1}{2000}\)
= 1 : 2000

Question (c).
50 paise to ₹ 5
Solution:
[Note : Unit of both quantities should be same.]
₹ 1 = 100 paise
∴ ₹ 5 = 500 paise
∴ Ratio of 50 paise to ₹ 5 = \(\frac{50 \text { paise }}{₹ 5}\)
= \(\frac{50 \text { paise }}{500 \text { paise }}\)
= \(\frac{1}{10}\)
= 1 : 10

2. Convert the following ratios to percentages.

Question (a).
3 : 4
Solution:
Given ratio = 3 : 4
∴ Percentage = (\(\frac{3}{4}\) × 100) %
= (3 × 25) %
= 75 %

Question (b).
2 : 3
Solution:
Given ratio = 2 : 3
∴ Percentage = (\(\frac{2}{3}\) × 100) %
= (\(\frac{200}{3}\)) %
= 66 \(\frac{2}{3}\)%

3. 72% of 25 students are interested in Mathematics. How many are not interested in Mathematics?
Solution:
Total number of students = 25
Students interested in Mathematics = 72%
∴ Students who are not interested in Mathematics = (100 – 72) %
= 28 %
Number of students who are not interested in Mathematics = 28% of 25
= \(\frac{28}{100}\) × 25
= \(\frac{28}{4}\)
= 7
Thus, 7 students are not interested in Mathematics.

4. A football team won 10 matches out of the total number of matches they played. If their win percentage was 40, then how many matches did they play in all ?
Solution:
Number of matches won by the football team = 10
Let x matches be played by the team.
∴ 40% of x = 10
∴ \(\frac{40}{100}\) × x = 10
∴ x = \(\frac{10 \times 100}{40}\)
= 25
Thus, the football team played 25 matches in all.

5. If Chameli had ₹ 600 left after spending 75% of her money, how much did she have in the beginning?
Solution:
Let Chameli had in the beginning ₹ x
Percentage of money spent by Chameli = 75 %
Percentage of money left with Chameli = (100 – 75)%
= 25%
But money left = ₹ 600 (Given)
∴ 25% of x = 600
∴ \(\frac{25}{100}\) × x = 600
∴ x = \(\frac{600 \times 100}{25}\)
∴ x = 2400
Thus, Chameli had ₹ 2400 in the beginning.

6. If 60% people in a city like cricket, 30% like football and the remaining like other games, then what per cent of the people like other games? If the total number of people is 50 lakh, find the exact number who like each type of game.
Solution:
Percentage of people who like cricket = 60 %
Percentage of people who like football = 30 %
∴ Percentage of people who like other games = [ 100 – (60 + 30)]%
= (100 – 90)%
= 10 %
Total number of people = 50,00,000 (Given)
Now,
People who like cricket
= 60% of 50,00,000
= \(\frac {1}{2}\) × 50,00,000
= 60 × 50000
= 3000000
= 30 lakh

People who like football
= 30% of 5000000
= \(\frac {30}{100}\) × 5000000
= 30 × 50000
= 1500000
= 15 lakh

People who like other games
= 10% of 5000000
= \(\frac {10}{100}\) × 5000000
= 500000
= 5 lakh
Thus, number of people who like
cricket = 30 lakh,
football = 15 lakh
and other games = 5 lakh

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 7 Cubes and Cube Roots InText Questions and Answers.

PSEB 8th Class Maths Solutions Chapter 7 Cubes and Cube Roots InText Questions

Try These (Textbook Page No. 111)

Find the one’s digit of the cube of each of the following numbers:
(i) 3331
(ii) 8888
(iii) 149
(iv) 1005
(v) 1024
(vi) 77
(vii) 5022
(viii) 53
Solution:

Sl. No.	Number	Number ending in	Units place digit of the cube
(i)	3331	1	1
(ii)	8888	8	2
(iii)	149	9	9
(iv)	1005	5	5
(v)	1024	4	4
(vi)	77	7	3
(vii)	5022	2	8
(viii)	53	3	7

Some interesting patterns: (Textbook Page No. 111)

Observe the following pattern of sums of odd numbers.

Try These (Textbook Page No. 111)

1. Express the following numbers as the sum of odd numbers using the above pattern ?
(a) 6³
(b) 8³
(c) 7³
Solution:
From above pattern, we can conclude n³ = [n(n – 1) + 1] + [n(n – 1) + 3] + [n(n – 1) + 5]… + n terms
(a) 6³
Here, n = 6, n- 1=5
6 (6 – 1) + 1 → 6 × 5 + 1 → 31

OR
= [6(6 – 1) + 1] + [6(6 – 1) + 3] + [6(6 – 1) + 5] + [6(6 – 1) + 7] + [6(6 – 1) + 9] + [6(6 – 1) + 11]
= (6 × 5 + 1) + (6 × 5 + 3) + (6 × 5 + 5) + (6 × 5 + 7) + (6 × 5 + 9) + (6 × 5 + 11)
= (30 + 1) + (30 + 3) + (30 + 5) + (30 + 7) + (30 + 9) + (30 + 11)
= 31 +33 + 35 + 37 + 39 + 41
= 216

(b) 8³
Here, n = 8, n – 1 = 7
8 (8 – 1) + 1 → 8 × 7 + 1 → 57

OR
= [8(8 – 1) + 1] + (8(8 – 1) + 3] + [8(8 – 1) + 5] + [8(8 – 1) + 7] + [8(8 – 1) + 9] + [8(8 – 1) + 11] + [8(8 – 1) + 13] + [8(8 – 1) + 15]
= (8 × 7 + 1) + (8 × 7 + 3) + (8 × 7 + 5) + (8 × 7 + 7) + (8 × 7 + 9) + (8 × 7 + 11) + (8 × 7 + 13) + (8 × 7 + 15)
= (56 + 1) + (56 + 3) + (56 + 5) + (56 + 7) + (56 + 9) + (56 + 11) + (56 + 13) + (56 + 15)
= 57 + 59 + 61 + 63 + 65 + 67 + 69 + 71
= 512

(c) 7³
Here, n = 7, n – 1 = 6
7 × 6 + 1 → 42 + 1 → 43

OR
= [7(7 – 1) + 1] + [7(7 – 1) + 3] + [7(7 – 1) + 5] + [7(7 – 1) + 7] + [7(7 – 1) + 9] + [7(7 – 1) + 11] + [7(7 – 1) + 13]
= (7 × 6 + 1) + (7 × 6 + 3) + (7 × 6 + 5) + (7 × 6 + 7) + (7 × 6 + 9) + (7 × 6 + 11) + (7 × 6 + 13)
= (42 + 1) + (42 + 3) + (42 + 5) + (42 + 7) + (42 + 9) + (42 + 11) + (42 + 13)
= 43 + 45 + 47 + 49 + 51 + 53 + 55
= 343

Consider the following pattern:
2³ – 1³ = 1 + 2 × 1 × 3
3³ – 2³ = 1 + 3 × 2 × 3
4³ – 3³ = 1 + 4 × 3 × 3
Using the above pattern, find the value of the following:
(i) 7³ – 6³
(ii) 12³– 11³
(iii) 20³ – 19³
(iv) 51³ – 50³
Solution:
From above pattern, we can conclude
n³ – (n – 1)³ = 1 + n × (n – 1) × 3
(i) 7³ – 6³ = 1 + 7 × 6 × 3
= 1 + 126
= 127

(ii) 12³ – 11³ = 1 + 12 × 11 × 3
= 1 + 396
= 397

(iii) 20³ – 19³ = 1 + 20 × 19 × 3
= 1 + 1140
= 1141

(iv) 51³ – 50³ = 1 + 51 × 50 × 3
= 1 + 7650
= 7651

Try These (Textbook Page No. 112)

1. Which of the following are perfect cubes?

Question (1).
400
Solution:
\(\begin{array}{l|l}
2 & 400 \\
\hline 2 & 200 \\
\hline 2 & 100 \\
\hline 2 & 50 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
400 = 2 × 2 × 2 × 2 × 5 × 5
Here, the prime factors 2 and 5 do not appear in triples.
∴ 2 × 5 × 5 is left over.
∴ 400 is not a perfect cube.

Question (2).
3375
Solution:
\(\begin{array}{l|l}
3 & 3375 \\
\hline 3 & 1125 \\
\hline 3 & 375 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
3375 = 3 × 3 × 3 × 5 × 5 × 5
Here, the prime factors 3 and 5 appear in triples.
No factor is left over.
∴ 3375 is a perfect cube.
3375 = 3³ × 5³

Question (3).
8000
Solution:
\(\begin{array}{l|l}
2 & 8000 \\
\hline 2 & 4000 \\
\hline 2 & 2000 \\
\hline 2 & 1000 \\
\hline 2 & 500 \\
\hline 2 & 250 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
8000 = 2 × 2 × 2 × 2 × 2 × 2 × 5 × 5 × 5
Here, the prime factors 2 and 5 appear in triples.
No factor is left over.
∴ 8000 is a perfect cube.
8000 = 2³ × 2³ × 5³

Question (4).
15625
Solution:
\(\begin{array}{l|l}
5 & 15625 \\
\hline 5 & 3125 \\
\hline 5 & 625 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
15625 = 5 × 5 × 5 × 5 × 5 × 5
Here, the prime factor 5 appear in triples.
No factor is left over.
∴ 15625 is a perfect cube.
15625 = 5³ × 5³

Question (5).
9000
Solution:
\(\begin{array}{l|l}
2 & 9000 \\
\hline 2 & 4500 \\
\hline 2 & 2250 \\
\hline 3 & 1125 \\
\hline 3 & 375 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
9000 = 2 × 2 × 2 × 3 × 3 × 5 × 5 × 5
Here, among the prime factors 2 and 5 appear in triples but 3 does not appear in triple.
3 × 3 is left over.
∴ 9000 is not a perfect cube.

Question (6).
6859
Solution:
\(\begin{array}{l|l}
19 & 6859 \\
\hline 19 & 361 \\
\hline 19 & 19 \\
\hline & 1
\end{array}\)
6859 = 19 × 19 × 19
Here, the prime factor 19 appears in triple.
No factor is left over.
∴ 6859 is a perfect cube.
6859 = 193

Question (7).
2025
Solution:
\(\begin{array}{l|l}
3 & 2025 \\
\hline 3 & 675 \\
\hline 3 & 225 \\
\hline 3 & 75 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
2025 = 3 × 3 × 3 × 3 × 5 × 5
Here, the prime factor 3 appears in triple, but 3 × 5 × 5 is left over.
∴ 2025 is not a perfect cube.

Question (8).
10648
Solution:
\(\begin{array}{r|l}
2 & 10648 \\
\hline 2 & 5324 \\
\hline 2 & 2662 \\
\hline 11 & 1331 \\
\hline 11 & 121 \\
\hline 11 & 11 \\
\hline & 1
\end{array}\)
10648 = 2 × 2 × 2 × 11 × 11 × 11
Here, the prime factors 2 and 11 appear in triples.
No factor is left over.
∴ 10648 is a perfect cube.
10648 = 2³ × 11³

Think, Discuss and Write (Textbook Page No. 113)

1. Check which of the following are perfect cubes:
(i) 2700
(ii) 16000
(iii) 64000
(iv) 900
(v) 125000
(vi) 36000
(vii) 21600
(viii) 10000
(ix) 27000000
(x) 1000
What pattern do you observe in these perfect cubes ?
Solution:
(i) 2700
The number is ending with two zeros. If a number ends with three zeros or a multiple of 3 zeros, it may be a perfect cube.
∴ 2700 is not a perfect cube.

(ii) 16000
The number is ending with three zeros.
So it may be a perfect cube.
But, 16 is not a perfect cube.
∴ 16000 is not a perfect cube.

(iii) 64000
The number is ending with three zeros.
So it may be a perfect cube.
64 is a perfect cube. (∵ 4³ = 64)
∴ 64000 is a perfect cube.

(iv) 900
The number is ending with two zeros.
So it is not a perfect cube.
∴ 900 is not a perfect cube.

(v) 125000
The number is ending with three zeros.
So it may be a perfect cube.
125 is a perfect cube. (∵ 5³ = 125)
∴ 125000 is a perfect cube.

(vi) 36000
The number is ending with three zeros.
So it may be a perfect cube.
But, 36 is not a perfect cube.
∴ 36000 is not a perfect cube.

(vii) 21600
The number is ending with two zeros.
So it is not a perfect cube.
∴ 21600 is not a perfect cube.

(viii) 10000
The number is ending with four zeros.
So it is not a perfect cube.
∴ 10000 is not a perfect cube.

(ix) 27000000
The number is ending with six zeros.
So it may be a perfect cube.
27 is a perfect cube. (∵ 3³ = 27)
∴ 27000000 is a perfect cube.

(x) 1000
The number is ending with three zeros.
So it may be a perfect cube.
1 is a perfect cube, (∵ 1³ = 1)
∴ 1000 is a perfect cube.

Think, Discuss and Write (Textbook Page No. 115)

1. State true or false for any integer m, m² < m³. Why ?
Solution:
It seems true, but not always true.
m × m = m² and m × m × m = m³
∴ m² < m³
e.g. if m = 1
∴ m² = 1² = 1 and m³ = 1³ = 1
∴ m² ≮  m³, but m² = m³
If m = (- 1)
∴ m² = (- 1)² = 1 and m³ = (- 1)³ = (- 1)
∴ m² ≮  m³, but m2 > m³
So the above statement is not always true.

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 9 Algebraic Expressions and Identities Ex 9.4 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities Ex 9.4

1. Multiply the binomials:

Question (i)
(2x + 5) and (4x – 3)
Solution:
= (2x + 5)(4x – 3)
= 2x(4x – 3) + 5 (4x – 3)
= 8x² – 6x + 20x – 15
= 8x² + 14x – 15

Question (ii)
(y – 8) and (3y – 4)
Solution:
= (y -8) (3y – 4)
= y (3y – 4) – 8 (3y – 4)
= 3y² – 4y – 24y + 32
= 3y² – 28y + 32

Question (iii)
(2.51 – 0.5m) and (2.51 + 0.5m)
Solution:
= (2.5l – 0.5m) (2.5l + 0.5m)
= 2.5l(2.5l + 0.5m) – 0.5m (2.5l + 0.5m)
= 6.25l² + 1.25lm – 1.25lm – 0.25m²
= 6.25l² – 0.25m²

Question (iv)
(a + 3b) and (x + 5)
Solution:
= (a + 3b) (x + 5)
= a (x + 5) + 3b (x + 5)
= ax + 5a + 3bx + 15b

Question (v)
(2pq + 3q²) and (3pq – 2q²)
Solution:
= (2pq + 3q²) (3pq – 2q²)
= 2pq (3pq – 2q²) + 3q² (3pq – 2q²)
= 6p²q² – 4pq³ + 9pq³ – 6q⁴
= 6p²q² + 5pq³ – 6q⁴

Question (vi)
(\(\frac {3}{4}\)a² + 3b²) and 4 (a² – \(\frac {2}{3}\)b²)
Solution:
= (\(\frac {3}{4}\)a² + 3b²) (4a² – \(\frac {8}{3}\)b²)
= \(\frac {3}{4}\)a⁴ (4a² – \(\frac {8}{3}\)b²) + 3b² (4a² – \(\frac {8}{3}\)b²)
= 3a₄ – 2a²b² + 12a²b² – 8b₄
= 3a⁴ + 10a²b² – 8b⁴

2. Find the product:

Question (i)
(5 – 2x) (3 + x)
Solution:
= 5 (3 + x) – 2x (3 + x)
= 15 + 5x – 6x – 2x²
= 15 – x – 2x²

Question (ii)
(x + 7y) (7x – y)
Solution:
= x(7x – y) + 7y (7x – y)
= 7x² – xy + 49xy – 7y²
= 7x² + 48xy – 7y²

Question (iii)
(a² + b) (a + b²)
Solution:
= a² (a + b²) + b (a + b²)
= a³ + a²b² + ab + b³

Question (iv)
(p² – q²) (2p + q)
Solution:
= p²(2p + q) – q²(2p + q)
= 2p³ + p²q – 2pq² – q³

3. Simplify:

Question (i)
(x² – 5) (x + 5) + 25
Solution:
= x² (x + 5) – 5 (x + 5) + 25
= x³ + 5x² – 5x – 25 + 25
= x³ + 5x² – 5x

Question (ii)
(a² + 5) (b³ + 3) + 5
Solution:
= a²(b³ + 3) + 5 (b³ + 3) + 5
= a²b³ + 3a² + 5b³ + 15 + 5
= a²b³ + 3a² + 5b³ + 20

Question (iii)
(t + s²)(t² – s)
Solution:
= t (t² – s) + s² (t² – s)
= t³ – st + s²t² – s³

Question (iv)
(a + b) (c – d) + (a – b) (c + d) + 2 (ac + bd)
Solution:
= a(c – d) + b(c – d) + a(c + d) – b(c + d) + 2 (ac + bd)
= ac – ad + bc – bd + ac + ad – bc – bd + 2ac + 2bd
= ac + ac + 2ac – ad + ad + bc – bc – bd – bd + 2 bd
= 4 ac

Question (v)
(x + y) (2x + y) + (x + 2y) (x – y)
Solution:
= x (2x + y) + y (2x + y) +x(x – y) + 2y (x – y)
= 2x² + xy + 2xy + y² + x² – xy + 2xy – 2y²
= 2x² + x² + xy + 2xy – xy + 2xy + y² – 2y²
= 3x² + 4xy – y²

Question (vi)
(x + y) (x² – xy + y²)
Solution:
= x (x² – xy + y²) + y (x² – xy + y²)
= x³ – x²y + xy² + x²y – xy² + y³
= x³ – x²y + x²y + xy² – xy² + y³
= x³ + y³

Question (vii)
(1.5x – 4y) (1.5x + 4y + 3) – 4.5x + 12y
Solution:
= 1.5x (1.5x + 4y + 3) – 4y (1.5x + 4y + 3) – 4.5x + 12y
= 2.25x² + 6xy + 4.5x – 6xy – 16y² – 12y – 4.5x + 12y
= 2.25x² + 6xy – 6xy + 4.5x – 4.5x – 16y² – 12y + 12y
= 2.25x² – 16y²

Question (viii)
(a + b + c) (a + b – c)
Solution:
= a (a + b – c) + b (a + b – c) + c (a + b – c)
= a² + ab – ac + ab + b² – bc + ac + bc – c²
= a² + ab + ab – ac + ac + b² – bc + bc – c²
= a² + 2ab + b² – c²
= a² + b² – c² + 2 ab

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 7 Cubes and Cube Roots Ex 7.2 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 7 Cubes and Cube Roots Ex 7.2

1. Find the cube root of each of the following numbers by prime factorisation method.

Question (i).
64
Solution:
\(\begin{array}{l|l}
2 & 64 \\
\hline 2 & 32 \\
\hline 2 & 16 \\
\hline 2 & 8 \\
\hline 2 & 4 \\
\hline 2 & 2 \\
\hline & 1
\end{array}\)
By prime factorisation,
64 = 2 × 2 × 2 × 2 × 2 × 2
∴ \(\sqrt[3]{64}\) = 2 × 2
= 4
Thus, cube root of 64 is 4.

Question (ii).
512
Solution:
\(\begin{array}{l|l}
2 & 512 \\
\hline 2 & 256 \\
\hline 2 & 128 \\
\hline 2 & 64 \\
\hline 2 & 32 \\
\hline 2 & 16 \\
\hline 2 & 8 \\
\hline 2 & 4 \\
\hline 2 & 2 \\
\hline & 1
\end{array}\)
By prime factorisation,
512 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2
∴ \(\sqrt[3]{512}\) = 2 × 2 × 2
= 8
Thus, cube root of 512 is 8.

Question (iii).
10648
Solution:
\(\begin{array}{r|l}
2 & 10648 \\
\hline 2 & 5324 \\
\hline 2 & 2662 \\
\hline 11 & 1331 \\
\hline 11 & 121 \\
\hline 11 & 11 \\
\hline & 1
\end{array}\)
By prime factorisation,
10648 = 2 × 2 × 2 × 11 × 11 × 11
∴ \(\sqrt[3]{10648}\) = 2 × 11
= 22
Thus, cube root of 10648 is 22.

Question (iv).
27000
Solution:
\(\begin{array}{l|l}
2 & 27000 \\
\hline 2 & 13500 \\
\hline 2 & 6750 \\
\hline 3 & 3375 \\
\hline 3 & 1125 \\
\hline 3 & 375 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
By prime factorisation
27000 = 2 × 2 × 2 × 3 × 3 × 3 × 5 × 5 × 5
∴ \(\sqrt[3]{27000}\) = 2 × 3 × 5
= 30
Thus, cube root of 27000 is 30.

Question (v).
15625
Solution:
\(\begin{array}{l|l}
5 & 15625 \\
\hline 5 & 3125 \\
\hline 5 & 625 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
By prime factorisation,
15625 = 5 × 5 × 5 × 5 × 5 × 5
∴ \(\sqrt[3]{15625}\) = 5 × 5
= 25
Thus, cube root of 15625 is 25.

Question (vi).
13824
Solution:
\(\begin{array}{l|l}
2 & 13824 \\
\hline 2 & 6912 \\
\hline 2 & 3456 \\
\hline 2 & 1728 \\
\hline 2 & 864 \\
\hline 2 & 432 \\
\hline 2 & 216 \\
\hline 2 & 108 \\
\hline 2 & 54 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
By prime factorisation,
13824 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3
∴ \(\sqrt[3]{13824}\) = 2 × 2 × 2 × 3
= 24

Question (vii).
110592
Solution:
\(\begin{array}{l|l}
2 & 110592 \\
\hline 2 & 55296 \\
\hline 2 & 27648 \\
\hline 2 & 13824 \\
\hline 2 & 6912 \\
\hline 2 & 3456 \\
\hline 2 & 1728 \\
\hline 2 & 864 \\
\hline 2 & 432 \\
\hline 2 & 216 \\
\hline 2 & 108 \\
\hline 2 & 54 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
By prime factorisation,
110592 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3
∴ \(\sqrt[3]{110592}\) = 2 × 2 × 2 × 2 × 3
= 48
Thus, cube root of 110592 is 48.

Question (viii).
46656
Solution:
\(\begin{array}{l|l}
2 & 46656 \\
\hline 2 & 23328 \\
\hline 2 & 11664 \\
\hline 2 & 5832 \\
\hline 2 & 2916 \\
\hline 2 & 1458 \\
\hline 3 & 729 \\
\hline 3 & 243 \\
\hline 3 & 81 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
By prime factorisation,
46656 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3 × 3 × 3 × 3
∴ \(\sqrt[3]{46656}\) = 2 × 2 × 3 × 3
= 36
Thus, cube root of 46656 is 36.

Question (ix).
175616
Solution:
\(\begin{array}{l|l}
2 & 175616 \\
\hline 2 & 87808 \\
\hline 2 & 43904 \\
\hline 2 & 21952 \\
\hline 2 & 10976 \\
\hline 2 & 5488 \\
\hline 2 & 2744 \\
\hline 2 & 1372 \\
\hline 2 & 686 \\
\hline 7 & 343 \\
\hline 7 & 49 \\
\hline 7 & 7 \\
\hline & 1
\end{array}\)
By prime factorisation,
175616 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 7 × 7 × 7
∴ \(\sqrt[3]{175616}\) = 2 × 2 × 2 × 7
= 56
Thus, cube root of 175616 is 56.

Question (x).
91125
Solution:
\(\begin{array}{l|l}
3 & 91125 \\
\hline 3 & 30375 \\
\hline 3 & 10125 \\
\hline 3 & 3375 \\
\hline 3 & 1125 \\
\hline 3 & 375 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
By prime factorisation,
91125 = 3 × 3 × 3 × 3 × 3 × 3 × 5 × 5 × 5
∴ \(\sqrt[3]{91125}\) =3 × 3 × 5
= 45
Thus, cube root of 91125 is 45.

2. State true or false.

Question (i).
Cube of any odd number is even.
Solution:
False, cube of any odd number is odd.

Question (ii).
A perfect cube does not end with two zeros.
Solution:
True, a perfect cube ending with zero will always have a triplet of zeros.

Question (iii).
If square of a number ends with 5, then its cube ends with 25.
Solution:
False, let us understand with an example.
15² = 15 × 15 = 225
15³ = 15 × 15 × 15 = 3375

Question (iv).
There is no perfect cube which ends with 8.
Solution:
False, let us understand with an example.
8 = 2³, 1728 = 12³

Question (v).
The cube of a two-digit number may be a three-digit number.
Solution:
False, let us take an example.
The smallest two-digit number is 10.
10³ = 1000
which is a four-digit number and not a three-digit number.

Question (vi).
The cube of a two-digit number may have seven or more digits.
Solution:
False, let us take an example.
The greatest two-digit number is 99.
99³ = 970299
which is a six-digit number.

Question (vii).
The cube of a single digit number may be a single digit number.
Solution:
True, let us take examples.
1³ = 1 and 2³ = 8

3. You are told that 1,331 is a perfect cube. Can you guess without factorisation what is its cube root? Similarly, guess the cube roots of 4913, 12167, 32768.
Solution:
Yes, we can guess without prime factorisation.
1331 : Separate given number into two groups.
1331 → 1 and 331
331 → Units place digit of 331 is 1.
∴ Unit place digit of cube root of 1331 = 1 (∵ 1³ = 1)
1 → 1³ = 1 and 2³ = 8
∴ Tens digit of cube root of 1331 = 1
Thus, the cube root of 1331 is 11.

(i) 4913 : Separate given number into two groups.
4913 → 4 and 913
913 → Units place digit of 913 is 3.
∴ Unit digit of cube root of 4913 = 7 (∵ 7³ = 343)
4 → 1³ = 1 and 2³ = 8
1 < 4 < 8 (∴ 1³ < 4 < 2³)
∴ The tens digit of cube root of 4913 = 1
Thus, the cube root of 4913 is 17.

(ii) 12167 : Separate given number into two groups.
12167 → 12 and 167
167 → Units place digit of 167 is 7.
∴ Unit digit of cube root of 12167 = 3
(∵ 3³ = 27)
12 → 2³ = 8 and 3³ = 27
8 < 12 < 27 (∵ 2³ < 12 < 3³)
∴ Tens place digit of cube root of 12167 = 2
Thus, the cube root of 12167 is 23.

(iii) 32768 : Separate given number into two groups.
32768 → 32 and 768
768 → Units place digit of 768 is 8.
∴ Unit digit of cube root of 32768 = 2 (∵ 2³ = 8)
32 → 3³ = 27 and 4³ = 64
27 < 32 < 64 (∵ 3³ < 32 < 4³)
∴ The tens digit of cube root of 32768 = 3
Thus, the cube root of 32768 is 32.

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 9 Algebraic Expressions and Identities Ex 9.3 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 9 Algebraic Expressions and Identities Ex 9.3

1. Carry out the multiplication of the expressions in each of the following pairs:

Question (i)
4p, q + r
Solution:
= 4p × (q + r)
= (4p × q) + (4p × r)
= 4pq + 4pr

Question (ii)
ab, a – b
Solution:
= ab × (a-b)
= (ab × a) – (ab × b)
= a²b – ab²

Question (iii)
a + b, 7a²b²
Solution:
= (a + b) × 7a²b²
= (a × 7a²b²) + (b × 7a²b²)
= 7 a³b² + 7a²b³

Question (iv)
a² – 9, 4a
Solution:
= (a² – 9) × 4a
= (a² × 4a) – (9 × 4a)
= 4a³ – 36a

Question (v)
pq + qr + rp, 0
Solution:
= (pq + qr + rp) × 0
= 0

2. Complete the table:

First expression	Second expression	Product
1. a	b + c + d	……………
2. x + y- 5	5xy	……………
3. P	6p2 – 7p + 5	…………..
4. 4p2q- q2	p2 – q2	…………..
5. a + b + c	abc	………….

Solution:
(i) a × (b + c + d)
= (a × b) + (a × c) + (a × d)
= ab + ac + ad

(ii) (x + y – 5) × 5xy
= (x × 5xy) + (y × 5xy) + [(- 5) × 5xy]
= 5x²y + 5xy² – 25xy

(iii) p × (6p² – 7p + 5)
= (p × 6p²) + [p × (- 7p)] + (p × 5)
= 6p³ – 7p² + 5p

(iv) 4p²q² × (p² – q²)
= (4p²q² × p²) + [4p²q² × (-q²)]
= 4p⁴q² – 4p²q⁴

(v) (a + b + c) × abc
= (a × abc) + (b × abc) + (c × abc)
= a²bc + ab²c + abc²

3. Find the product:

Question (i)
(a²) × (2a²²) × (4a²⁶)
Solution:
= (1 × 2 × 4) × a² × a²² × a²⁶
= 8 × a⁵⁰
= 8a⁵⁰

Question (ii)
(\(\frac {2}{3}\)xy) × (\(\frac {-9}{10}\)x²y²)
Solution:
= \(\frac {2}{3}\) × (\(\frac {-9}{10}\)) × xy × x²y²
= \(\frac {-2}{3}\) × \(\frac {9}{10}\) × x³y³
= \(\frac {-3}{5}\)x³y³

Question (iii)
(\(\frac {-10}{3}\)pq³) × (\(\frac {6}{5}\)p³q)
Solution:
= [(\(\frac {-10}{3}\)) × \(\frac {6}{5}\)] × pq³ × p³q
= – \(\frac {10}{3}\) × \(\frac {6}{5}\) × p⁴q⁴
= – 4p⁴q⁴

Question (iv)
x × x² × x³ × x⁴
Solution:
= (1 × 1 × 1 × 1) × x × x² × x³ × x⁴
= (1) × x¹⁰
= x¹⁰

4.

Question (a)
Simplify 3x(4x – 5) + 3 and find its value for
(i) x = 3
(ii) x = \(\frac {1}{2}\)
Solution:
3x (4x- 5) + 3
= (3x × 4x) – (3x × 5) + 3
= 12x¹⁰ – 15x + 3

(i) When x = 3, then
12x² – 15x + 3
= 12 (3)² – 15(3) + 3
= 12 (9) – 15 (3) + 3
= 108 -45 + 3
= 111 – 45
= 66

(ii) x = \(\frac {1}{2}\), then
12x² – 15x + 3
= 12(\(\frac {1}{2}\))² – 15(\(\frac {1}{2}\)) + 3
= 12(\(\frac {1}{4}\)) – 15(\(\frac {1}{2}\)) + 3
= 3 – \(\frac {15}{2}\) + 3
= 6 – \(\frac {15}{2}\)
= \(\frac{12-15}{2}\)
= \(\frac {-3}{2}\)

Question (b)
Simplify a (a2 + a + 1) + 5 and find its values for
(i) a = 0 (ii) a = 1 (iii) a = (-1)
Solution:
a (a² + a + 1) + 5
= (a × a²) + (a × a) + (a × 1) + 5
= a³ + a² + a + 5

(i) When a = 0, then
a³ + a² + a + 5
= (-1)³ + (0)³ + (0) + 5
= 0 + 0 + 0 + 5
= 5

(ii) a = 1, then
a³ + a² + a + 5
= (1)³ + (1)² + (1) + 5
= 1 + 1 + 1 + 5
= 8

(iii) a = (-1), then
a³ + a² + a + 5
= (-1)³ + (-1)² + (-1) + 5
= (-1) + (1) + (-1) + 5
= 6 – 2 = 4

5.

Question (a)
Add : p(p – q), q(q – r) and r(r – p)
Solution:
[p(p-q)] + [q(q-r)] + [r(r-p)]
= p² – pq + q² – qr + r² – rp
= p² + q² + r² – pq – qr – rp

Question (b)
Add : 2x(z – x – y) and 2y(z – y – x)
Solution:
[2x (z – x – y)] + [2y (z – y – x)]
= 2xz – 2x² – 2xy + 2yz – 2y² – 2xy
= – 2x² – 2y² – 2xy – 2xy + 2yz + 2xz
= – 2x² – 2y² – 4xy + 2yz + 2xz

Question (c)
Subtract : 31(l – 4m + 5n) from 4l(10n – 3m + 2l)
Solution:
[4l(10n – 3m + 21)] – [3l(l – 4m + 5n)]
= [40ln – 12lm + 8l²] – [3l² – 12lm + 15ln]
= 40ln – 12lm + 8l² – 3l² + 12lm – 15ln
= 40ln – 15ln – 12lm + 12lm + 8l² – 3l²
= 25ln + 0lm + 5l²
= 25ln + 5l²

Question (d)
Subtract : 3a(a + b + c) – 2b(a – b + c) from 4c(- a + b + c)
Solution:
[4c (- a + b + c)] – [3a (a + b + c) – 2b (a – b + c)]
= [- 4ac + 4bc + 4c²]
– [3a² + 3ab + 3ac – 2ab + 2b² – 2bc]
= – 4ac + 4be + 4c² – 3a² – 3ab – 3ac + 2ab – 2b² + 2bc
= – 3a² – 2b² + 4c² – 3ab + 2ab + 4bc + 2bc – 4ac – 3ac
= – 3a² – 2b² + 4c² – ab + 6bc – 7ac

Punjab State Board PSEB 8th Class Maths Book Solutions Chapter 7 Cubes and Cube Roots Ex 7.1 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 8 Maths Chapter 7 Cubes and Cube Roots Ex 7.1

1. Which of the following numbers are not perfect cubes ?

Question (i).
216
Solution:
216
\(\begin{array}{l|l}
2 & 216 \\
\hline 2 & 108 \\
\hline 2 & 54 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
216 = 2 × 2× 2 × 3 × 3 × 3
Here, the prime factors 2 and 3 appear in a group of three (triples).
∴ 216 is a perfect cube.
216 = 2³ × 3³

Question (ii).
128
Solution:
\(\begin{array}{l|l}
2 & 128 \\
\hline 2 & 64 \\
\hline 2 & 32 \\
\hline 2 & 16 \\
\hline 2 & 8 \\
\hline 2 & 4 \\
\hline 2 & 2 \\
\hline & 1
\end{array}\)
128 = 2 × 2 × 2 × 2 × 2 × 2 × 2
Here, the prime factor 2 does not appear in a group of three.
∴ 128 is not a perfect cube.

Question (iii).
1000
Solution:
\(\begin{array}{l|l}
2 & 1000 \\
\hline 2 & 500 \\
\hline 2 & 250 \\
\hline 5 & 125 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
1000 = 2 × 2 × 2 × 5 × 5 × 5
Here, the prime factors 2 and 5 appear in a group of three.
∴ 1000 is a perfect cube.
1000 = 2³ × 5³

Question (iv).
100
Solution:
\(\begin{array}{l|l}
2 & 100 \\
\hline 2 & 50 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
100 = 2 × 2 × 5 × 5
Here, the prime factors 2 and 5 do not appear in a group of three.
∴ 100 is not a perfect cube.

Question (v).
46656
Solution:
\(\begin{array}{l|l}
2 & 46656 \\
\hline 2 & 23328 \\
\hline 2 & 11664 \\
\hline 2 & 5832 \\
\hline 2 & 2916 \\
\hline 2 & 1458 \\
\hline 3 & 729 \\
\hline 3 & 243 \\
\hline 3 & 81 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
46656 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3 × 3 × 3 × 3
Here, the prime factors 2 and 3 appear in a group of three.
∴ 46656 is a perfect cube.
46656 = 2³ × 2³ × 3³ × 3³

2. Find the smallest number by which each of the following numbers must be multiplied to obtain a perfect cube:

Question (i).
243
Solution:
\(\begin{array}{l|l}
3 & 243 \\
\hline 3 & 81 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
243 = 3 × 3 × 3 × 3 × 3
Here, the prime factor 3 does not appear in a group of three.
∴ 243 is not a perfect cube.
(243) × 3 = (3 × 3 × 3 × 3 × 3) × 3
∴ 729 = 3³ × 3³
Thus, 3 is the smallest number by which 243 must be multiplied to get a perfect cube.

Question (ii).
256
Solution:
\(\begin{array}{l|l}
2 & 256 \\
\hline 2 & 128 \\
\hline 2 & 64 \\
\hline 2 & 32 \\
\hline 2 & 16 \\
\hline 2 & 8 \\
\hline 2 & 4 \\
\hline 2 & 2 \\
\hline & 1
\end{array}\)
256 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2
Here, the prime factor 2 does not appear in a group of three.
∴ 256 is not a perfect cube.
(256) × 2
= (2 × 2 × 2 × 2 × 2 × 2 × 2 × 2) × 2
∴ 512 = 2³ × 2³ × 2³
Thus, 2 is the smallest number by which 256 must be multiplied to get a perfect cube.

Question (iii).
72
Solution:
\(\begin{array}{l|l}
2 & 72 \\
\hline 2 & 36 \\
\hline 2 & 18 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
72 = 2 × 2 × 2 × 3 × 3
Here, the prime factor 3 does not appear in a group of three.
∴ 72 is not a perfect cube.
(72) × 3
= (2 × 2 × 2 × 3 × 3) × 3
∴ 216 = 2³ × 3³
Thus, 3 is the smallest number by which 72 must be multiplied to get a perfect cube.

Question (iv).
675
Solution:
\(\begin{array}{l|l}
3 & 675 \\
\hline 3 & 225 \\
\hline 3 & 75 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
∴ 675 = 3 × 3 × 3 × 5 × 5
Here, the prime factor 5 does not appear in a group of three.
∴ 675 is not a perfect cube.
(675) × 5
= (3 × 3 × 3 × 5 × 5) × 5
∴ 3375 = 3³ × 5³
Thus, 5 is the smallest number by which 675 must be multiplied to get a perfect cube.

Question (v).
100
Solution:
\(\begin{array}{l|l}
2 & 100 \\
\hline 2 & 50 \\
\hline 5 & 25 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
100 = 2 × 2 × 5 × 5
Here, the prime factors 2 and 5 do not appear in a group of three.
∴ 100 is not a perfect cube.
(100) × 2 × 5 = (2 × 2 × 5 × 5) × 2 × 5
∴ 1000 = 2³ × 5³
Thus, 10 is the smallest number by which 100 must be multiplied to get a perfect cube.

3. Find the smallest number by which each of the following numbers must be divided to obtain a perfect cube:

Question (i).
81
Solution:
\(\begin{array}{l|l}
3 & 81 \\
\hline 3 & 27 \\
\hline 3 & 9 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
81 = 3 × 3 × 3 × 3
Here, the prime factor 3 is left over after making triples of 3.
∴ 81 is not a perfect cube.
(81) ÷ 3 = (3 × 3 × 3 × 3) ÷ 3
∴ 27 = 3 × 3 × 3 = 33
Thus, 3 is the smallest number by which 81 must be divided to get a perfect cube.

Question (ii).
128
Solution:
\(\begin{array}{l|l}
2 & 128 \\
\hline 2 & 64 \\
\hline 2 & 32 \\
\hline 2 & 16 \\
\hline 2 & 8 \\
\hline 2 & 4 \\
\hline 2 & 2 \\
\hline & 1
\end{array}\)
128 = 2 × 2 × 2 × 2 × 2 × 2 × 2
Here, the prime factor 2 is left over after making triples of 2.
∴ 128 is not a perfect cube.
(128) ÷ 2
= (2 × 2 × 2 × 2 × 2 × 2 × 2) ÷ 2
∴ 64 = 2 × 2 × 2 × 2 × 2 × 2
= 2³ × 2³
Thus, 2 is the smallest number by which 128 must be divided to get a perfect cube.

Question (iii).
135
Solution:
\(\begin{array}{l|l}
3 & 135 \\
\hline 3 & 45 \\
\hline 3 & 15 \\
\hline 5 & 5 \\
\hline & 1
\end{array}\)
135 = 3 × 3 × 3 × 5
Here, the prime factor 5 is left over after making triples of 3.
∴ 135 is not a perfect cube.
(135) ÷ 5 = (3 × 3 × 3 × 5) ÷ 5
∴ 27 = 3 × 3 × 3
= 3³
Thus, 5 is the smallest number by which 135 must be divided to get a perfect cube.

Question (iv).
192
Solution:
\(\begin{array}{l|l}
2 & 192 \\
\hline 2 & 96 \\
\hline 2 & 48 \\
\hline 2 & 24 \\
\hline 2 & 12 \\
\hline 2 & 6 \\
\hline 3 & 3 \\
\hline & 1
\end{array}\)
192 = 2 × 2 × 2 × 2 × 2 × 2 × 3
Here, the prime factor 3 is left over after making triples of 2.
∴ 192 is not a perfect cube.
(192) ÷ 3
= (2 × 2 × 2 × 2 × 2 × 2 × 3) ÷ 3
∴ 64 = 2 × 2 × 2 × 2 × 2 × 2
= 2³ × 2³
Thus, 3 is the smallest number by which 192 must be divided to get a perfect cube.

Question (v).
704
Solution:
\(\begin{array}{l|l}
2 & 704 \\
\hline 2 & 352 \\
\hline 2 & 176 \\
\hline 2 & 88 \\
\hline 2 & 44 \\
\hline 2 & 22 \\
\hline 11 & 11 \\
\hline & 1
\end{array}\)
704 = 2 × 2 × 2 × 2 × 2 × 2 × 11
Here, the prime factor 11 is left over after making triples of 2.
∴ 704 is not a perfect cube.
(704) ÷ 11
= (2 × 2 × 2 × 2 × 2 × 2 × 11) ÷ 11
∴ 64 = 2 × 2 × 2 × 2 × 2 × 2
= 2³ × 2³
Thus, 11 is the smallest number by which 704 must be divided to get a perfect cube.

4. Parikshit makes a cuboid of plasticine of sides 5 cm, 2 cm, 5 cm. How many such cuboids will he need to form a cube ?
Solution:
Sides of the cuboid are 5 cm, 2 cm and 5 cm (Given).
∴ Volume of the cuboid = l × b × h
= 5 cm × 2 cm × 5 cm
To form it as a cube, its dimensions should be in the group of triplets.
Here, the prime factors 2 and 5 are not in group of three.
∴ Volume of the required cube
= (5 cm × 5 cm × 2 cm) × 5 cm × 2 cm × 2 cm
= (5³ × 2³) cm³
Thus, Parikshit needed 5 × 2 × 2 = 20 cuboids to form a cube.