Whole Numbers
Exercise 2.2
Examples for Practice
1). Find the sum by suitable rearrangement.
a). 837 + 208 + 363
837 + 208 + 363 = (837 + 363) + 208
= 1200 + 208
= 1408
Ans: 837 + 208 + 363 = 1,408
b). 1962 + 453 + 1538 + 647
1962 + 453 + 1538 + 647 = (1962 + 1538) + (453 + 647)
= 3500 + (453 + 647)
= 3500 + 1100
= 4600
Ans: 1962 + 453 + 1538 + 647 = 4,600
2). Find the product by suitable rearrangement.
a). 2 X 1768 X 50
2 X 1768 X 50 = (2 X 50) X 1768
= 100 X 1768
= 176800
Ans: 2 X 1768 X 50 = 1,76,800
b). 4 X 166 X 25
4 X 166 X 25 = (4 X 25) X 166
= 100 X 166
= 16600
Ans : 4 X 166 X 25 = 16,600
c). 8 X 291 X 125
8 X 291 X 125 = (8 X 125) X 291
= 1000 X 291
= 291000
Ans: 8 X 291 X 125 = 2,91,000
d). 625 X 279 X 16
625 X 279 X 16 = (625 X 16) X 279
= 10000 X 279
= 2790000
Ans: 625 X 279 X 16 = 27,90,000
e). 285 X 5 X 60
285 X 5 X 60 = 285 X (5 X 60)
= 285 X 300
= 85500
285 X 5 X 60 = 85,500
f). 125 X 40 X 8 X 25
Method I
125 X 40 X 8 X 25 = (125 X 40) X (8 X 25)
= 5000 X 200
= 1000000
Ans: 125 X 40 X 8 X 25 = 10,00,000
Method II
125 X 40 X 8 X 25 = (125 X 8) X (40 X 25)
= 1000 X 1000
= 1000000
Ans: 125 X 40 X 8 X 25 = 10,00,000
3). Find the value of the following:
a). 297 X 17 + 297 X 3
297 X 17 + 297 X 3 = 297 X 17 + 297 X 3
= 297 ( 17 + 3)
= 297 X 20
= 5940
Ans: 297 X 17 + 297 X 3 = 5,940
b). 54279 X 92 + 8 X 54279
54279 X 92 + 8 X 54279 = 54279 X 92 + 8 X 54279
= 54279 ( 92 + 8)
= 54279 X 100
= 5427900
Ans: 54279 X 92 + 8 X 54279 = 54,27,900
c). 81265 X 169 – 81265 X 69
81265 X 169 – 81265 X 69 = 81265 X 169 – 81265 X 69
= 81265 X (169 – 69)
= 81265 X 100
= 8126500
Ans: 81265 X 169 – 81265 X 69 = 81,26,500
d). 3845 X 5 X 782 + 769 X 25 X 218
3845 X 5 X 782 + 769 X 25 X 218
= (3845 X 5) X 782 + (769 X 25) X 218
= 19225 X 782 + 19225 X 218
= 19225 X (782 + 218)
= 19225 X 1000
= 19225000
Ans: 3845 X 5 X 782 + 769 X 25 X 218 = 1,92,25,000
4). Find the product using suitable properties.
a). 738 X 103
738 X 103 = 738 X (100 + 3)
= 738 X 100 + 738 X 3
= 73800 + 2214
= 76014
Ans: 738 X 103 = 76,014
b). 854 X 102
854 X 102 = 854 X (100 + 2)
= 854 X 100 + 854 X 2
= 85400 + 1708
= 87108
Ans: 854 X 102 = 87,108
c). 258 X 1008
258 X 1008 = 258 X (1000 + 8)
= 258 X 1000 + 258 X 8
= 258000 + 2064
= 260064
Ans: 258 X 1008 =2,60,064
d). 1005 X 168
1005 X 168 = (1000 + 5) X 168
= 1000 X 168 + 5 X 168
= 168000 + 840
= 168840
Ans: 1005 X 168 =168840
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?
Petrol filled in the tank on Monday = 40 litres
Petrol filled next day = 50 litres
Cost of the petrol = Rs 44 per litre
Total spend on the petrol =?
Total petrol filled in the car= 40 + 50
= 90 litres
Cost of the total petrol = 90 X 44
= Rs 3960
Ans: Total spend on the petrol = Rs 3,960.
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 rupees 45 per litre, how much money is due to the vendor per day?
Milk supplied in the morning = 32 litres
Milk supplied in the evening = 68 litres
Cost of the milk = Rs 45 per litre
Total milk supplied is = 32 + 68
= 100
Total money spend on the milk = 100 X 45
= 4500
Ans: Total money spend on the milk= Rs 4,500.
7). Match the following:
i). 425 X 136 = 425 X (6+30+100) a). commutative under
multiplication
ii). 2 X 49 X 50 = 2 X 50X 49 b). commutative under
addition
iii). 80 + 2005 + 20 = 80 + 20 + 2005 c). Distributivity of
multiplication
Answers:
i). 425 X 136 = 425 X (6+30+100 – Distributivity of multiplication
ii). 2 X 49 X 50 = 2 X 50X 49 – commutative under multiplication
iii). 80 + 2005 + 20 = 80 + 20 + 2005 – commutative under addition.
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