Chapter - 2 Whole Numbers

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Q
Whole Numbers

Question:

1. Find the sum by suitable rearrangement:

(a) 837 + 208 + 363        (b) 1962 + 453 + 1538 + 647

 

Solution: (a) 837 + 208 + 363

(837 + 363) + 208 

1200 + 208 = 1408

 

(b) 1962 + 453 + 1538 + 647

(1962 + 1538) + (453 + 647)

3500 + 1100 = 4600

 

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 

 

Solution: (a) 2 x 1768 × 50

= 2× 50 × 1768 

= 100 × 1768

= 176800

 

(b) 4 x 166 x 25

= 4 x 25 × 166

= 100 x 166

= 16600

 

(c) 8 x 291 × 125

= 8 × 125 × 291

= 1000 × 291

= 291000

 

(d) 625 × 279 × 16

= 625 x 16 x 279

= 10000 x 279

= 2790000

 

(e)  285 × 5 × 60

= 285 × 300

= 85500

 

(f) Given 125 × 40 × 8 × 25

= 125 x 8 x 40 x 25

= 1000 x 1000

= 1000000

 

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

 

Solution: (a) 297 × 17 + 297 × 3  

= 297 × (17 + 3)

= 297 × 20

= 5940

 

(b) 54279 × 92 + 8 × 54279

= 54279 × (92 + 8)

= 54729 × 100

= 5472900

 

(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)

= 3845 × 5 × 1000

= 19225 × 1000

= 19225000

 

4. Find the product using suitable properties.

(a) 738 × 103    (b) 854 × 102    (c) 258 × 1008    (d) 1005 × 168

 

Solution: (a) 738 x 103

= 738 x (100 + 3)

Using distributive property.

= 738 x 100+ 738 x 3

= 73800 + 2214

= 76014

 

(b) 854 x 102

= 854 x (100 + 2)

Using distributive property

= 854 × 100 + 854 × 2

= 85400 + 1708

= 87108

 

(c) 258 × 1008

= 258 x (1000 + 8)

Using distributive property.

= 258 x 1000 + 258 × 8

= 258000 + 2064

= 260064

 

(d) 1005 × 168

= (1000 + 5) × 168

Using distributive property.

= 1000×168 + 5 × 168

= 168000 + 840

= 168840

 

5. A taxidriver 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 โ‚น 44 per litre, how much did he spend in all on petrol?

 

Solution: Petrol filled on Monday = 40 litres.

Petrol filled on the next day = 50 litres.

Total petrol filled = 40 + 50 = 90 liters.

Petrol cost = โ‚น 44 per litre {Given}

Total money spend = โ‚น 44 x 90

Total money spend = โ‚น 3960

 

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 โ‚น 45 per litre, how much money is due to the vendor per day?

 

Solution: 

Given:

Milk supplied quantity in the morning = 32 litres.

Milk supplied quantity in the evening = 68 litres.

Milk Cost = โ‚น 45 per litre

Cost of the milk supplied in the morning = โ‚น 45 x 32

Cost of the milk supplied in the evening = โ‚น 45 x 68

Total earning of the vendor = โ‚น 45 x 32 + โ‚น 45 x 68

Total earning of the vendor = โ‚น 45 x (32 + 68)

Total earning of the vendor = โ‚น 45 x 100

Total earning of the vendor = โ‚น 4500

 

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

 

Solution: 

(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.

Answer:


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