Exercise 1.3 (Multiplication of Decimal Numbers)

Multiplication of Decimal Numbers

Exercise 1.3

1. Find the product of the following

(i) 0.5 × 3

5 × 3 = 15

∴ 0.5 × 3 = 1.5

(ii) 3.75 × 6

375 × 6 = 2250

3.75 × 6 = 22.50

(iii) 50.2 × 4

502 × 4 = 2008

50.2 × 4 = 200.8

(iv) 0.03 × 9

3 × 9 = 27

0.03 × 9 = 0.27

(v) 453.03 × 7

45303 × 7 = 317121

453.03 × 7= 3171.21

(vi) 4 × 0.7

4 × 7 = 28

4 × 0.7 = 2.8

2. Find the area of the parallelogram whose base is 6.8 cm and height is 3.5 cm.

Solution:  

Base of the parallelogram b = 6.8 cm

Height of the parallelogram h = 3.5 cm

Area of the parallelogram A = b ×  h sq.units = 6.8 × 3.5 cm²

Area of the parallelogram = 23.80 cm²

3. Find the area of the rectangle whose length is 23.7 cm and breadth is 15.2 cm.

Solution:  

Length of the rectangle l = 23.7 cm

Breadth of the rectangle b = 15.2 cm

Area of the rectangle A = l × b sq.units

= 23.7 × 15.2 cm²

Area of the rectangle = 360.24 cm²

4. Multiply the following

(i) 2.57 × 10 = 25.7

(ii) 0.51 × 10 = 5.1

(iii) 125.367 × 100 = 12536.7

(iv) 34.51 ×100 = 3451

(v) 62.735 × 100 = 6273.5

(vi) 0.7 × 10 = 7.0

(vii) 0.03 × 100 = 3

 (viii) 0.4 ×1000 = 400

5. A wheel of a baby cycle covers 49.7 cm in one rotation. Find the distance covered in 10 rotations.

Solution:

Length covered in 1 rotation = 49.7 cm

Length covered in 10 rotations = 49.7 × 10 cm = 497 cm

6. A picture chart costs ₹ 1.50. Radha wants to buy 20 charts to make an album. How much does she have to pay?

Solution:

Cost of 1 chart = ₹ 1.50

Cost of 20 charts = ₹ 1.50 × 20 = ₹ 30.00

Cost of 20 charts = ₹ 30

7. Find the product of the following.

(i) 3.6 × 0.3

 36 × 3 = 108

 3.6 × 0.3 = 1.08

(ii) 52.3 × 0.1

 523 × 1 = 523

 52.3 × 0.1 = 5.23

(iii) 537.4 × 0.2

 5374 × 2 = 10748

 537.4 × 0.2 = 107.48

(iv) 0.6 × 0.06

 6 × 6 = 36

 0.6 × 0.06 = 0.036

 (v) 62.2 × 0.23

 622 × 23 = 14306

 62.2 × 0.23 = 14.306.

(vi) 1.02 × 0.05

 102 × 5 = 510

 1.02 × 0.05 = 0.0510

(vii) 10.05 × 1.05

 1005 × 105 = 105525

 10.05 × 1.05 = 10.5525

(viii) 101.01 × 0.01

 10101 × l = 10101

 101.01 × 0.01 = 1.0101

(ix) 100.01 ×1.1

 10001 × 11 = 110011

 100.01 × 1.1 = 110.011

Objective type questions

8. 1.07 × 0.1 ________

(i) 1.070

(ii) 0.107

 (iii) 10.70

 (iv) 11.07

[Answer: (ii) 0.107]

 Solution: 107 × 1 = 107

 1.07 × 0.1 = 0.107 

9. 2.08 × 10 = ________

(i) 20.8

(ii) 208.0

(iii) 0.208

(iv) 280.0

[Answer: (i) 20.8]

 Solution: 208 × 10 = 2080

 2.08 × 10 = 20.80 = 20.8 

10. A frog jumps 5.3 cm in one jump. The distance travelled by the frog in 10 jumps is

 ---------

(i) 0.53 cm

(ii) 530 cm

(iii) 53.0 cm

(iv) 53.5 cm

[Answer: (iii) 53.0 cm]

 Solution: 53 × 10 = 530

 5.3 × 10 = 53.0

ANSWERS:

Exercise 1.3

1. (i) 1.5 (ii) 22.50 (iii) 200.8 (iv) 0.27 (v) 3171.21 (vi) 2.8

2. 23.80 sq.cm

3. 360.24 sq.cm

4. (i) 25.7 (ii) 5.1 (iii) 12536.7 (iv) 3451 (v) 6273.5 (vi) 7.0 (vii) 3 (viii) 400

5. 497cm

6. ₹ 30

7. (i) 1.08 (ii) 5.23 (iii) 107.48 (iv) 0.036 (v) 14.306 (vi) 0.051 (vii) 10.5525 (viii) 1.0101 (ix) 110.011

 Objective type questions

8. (ii) 0.107

9. (i) 20.8

10. (iii) 53.0 cm