## Chapter 2 Whole Numbers Exercise 2.2

**Question 1: Find the sum by suitable rearrangement:**

a) 837 + 208 + 363

b) 1962 + 453 + 1538 + 647

Answer:

a) 837 + 208 + 363

b) 1962 + 453 + 1538 + 647

Answer:

a)

= 837 + 208 + 363

= (837 + 363) + 208

= 1200 + 208

= 1408

b)

= 1962 + 453 + 1538 + 647

= (1962 + 1538) + (453 + 647)

= 3500 + 1100

= 4600

**Question 2: Find the product by suitable rearrangement:**

a) 2 × 1768 × 50

b) 4 × 166 × 25

c) 8 × 291 × 125

d) 625 × 279 × 16

e) 285 × 5 × 60

f) 125 × 40 × 8 × 25

Answer:

a) 2 × 1768 × 50

b) 4 × 166 × 25

c) 8 × 291 × 125

d) 625 × 279 × 16

e) 285 × 5 × 60

f) 125 × 40 × 8 × 25

Answer:

a)

= 2 × 1768 × 50

= (2 × 50) × 1768

= 100 × 1768

= 176800

b)

= 4 × 166 × 25

= (4 × 25) × 166

= 100 × 166

= 16600

c)

= 8 × 291 × 125

= (8 × 125) × 291

= 1000 × 291

= 291000

d)

= 625 × 279 × 16

= (625 × 16) × 279

= 10000 × 279

= 2790000

e)

= 285 × 5 × 60

= 285 × (60 × 5)

= 285 × 300

= 85500

f)

125 × 40 × 8 × 25

= (125 × 8) × (40 × 25)

= 1000 × 1000

= 1000000

**Question 3: Find the value of the following:**

a) 297 × 17 + 297 × 3

b) 54279 × 92 + 8 × 54279

c) 81265 × 169 - 81265 × 69

d) 3845 × 5 × 782 + 769 × 25 × 218

Answer:

a) 297 × 17 + 297 × 3

b) 54279 × 92 + 8 × 54279

c) 81265 × 169 - 81265 × 69

d) 3845 × 5 × 782 + 769 × 25 × 218

Answer:

a)

= 297 × 17 + 297 × 3

= 297 × (17 + 3)

= 297 × 20

= 5940

b)

= 54279 × 92 + 8 × 54279

= 54279 × 92 + 54279 × 8

= 54279 × (92 + 8)

= 54279 × 100

= 5427900

c)

= 81265 × 169 - 81265 × 69

= 81265 × (169 - 69)

= 81265 × 100

= 8126500

d)

= 3845 × 5 × 782 + 769 × 25 × 218

= 3845 × 5 × 782 + 769 × 5 × 5 × 218

= 3845 × 5 × 782 + 3845 × 5 × 218

= 3845 × 5 × (782 + 218)

= 19225 × 1000

= 19225000

**Question 4: Find the product using suitable properties.**

a) 738 × 103

b) 854 × 102

c) 258 × 1008

d) 1005 × 168

Answer:

a) 738 × 103

b) 854 × 102

c) 258 × 1008

d) 1005 × 168

Answer:

a)

= 738 × 103

= 738 × (100 + 3)

= 738 × 100 + 738 × 3 (distributive property)

= 73800 + 2214

= 76014

b)

= 854 × 102

= 854 × (100 + 2)

= 854 × 100 + 854 × 2 (distributive property)

= 85400 + 1708

= 87108

c)

= 258 × 1008

= 258 × (1000 + 8)

= 258 × 1000 + 258 × 8 (distributive property)

= 258000 + 2064

= 260064

d)

= 1005 × 168

= (1000 + 5) × 168

= 1000 × 168 + 5 × 168 (distributive property)

= 168000 + 840

= 168840

**Question 5: A taxi driver filled his car petrol tank with 40 litres of petrol on Monday. The next day, he filled the tank with 50 litres of petrol. If the petrol costs ₹44 per litre, how much did he spend in all on petrol?**

Answer:

Answer:

Petrol filled on Monday = 40 litres

Petrol filled on Tuesday = 50 litres

Total petrol filled = 40 + 50 = 90 litres

Cost of petrol per litre = ₹ 44

Total money spent = ?

= 44 × 90

= ₹3960

Therefore, the taxi driver spent ₹3960 on petrol for 2 days i.e. Monday and Tuesday.

**Question 6: A vendor supplies 32 litres of milk to a hotel in the morning and 68 litres of milk in the evening. If the milk costs ₹45 per litre, how much money is due to the vendor per day?**

Answer:

Answer:

Milk supplied in the morning = 32 litres

Milk supplied in the evening = 68 litres

Total milk supplied in the day = 32 + 68 = 100 litres

Cost of milk per litre = ₹ 45

Total cost of milk per day = ?

= 45 × 100

= ₹ 4500

Therefore, the money is due to the vendor per day is ₹ 4500

**Question 7: Match the following:**

i) 425 × 136 = 425 × (6 + 30 + 100) a) Commutativity under multiplication.

ii) 2 × 49 × 50 = 2 × 50 × 49 b) Commutativity under addition.

iii) 80 + 2005 + 20 = 80 + 20 + 2005 c) Distributivity of multiplication over addition.

Answer:

i) 425 × 136 = 425 × (6 + 30 + 100) a) Commutativity under multiplication.

ii) 2 × 49 × 50 = 2 × 50 × 49 b) Commutativity under addition.

iii) 80 + 2005 + 20 = 80 + 20 + 2005 c) Distributivity of multiplication over addition.

Answer:

i) 425 × 136 = 425 × (6 + 30 + 100) - c) Distributivity of multiplication over addition.

ii) 2 × 49 × 50 = 2 × 50 × 49 - a) Commutativity under multiplication.

iii) 80 + 2005 + 20 = 80 + 20 + 2005 - b) Commutativity under addition.

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