RS Aggarwal Solutions: Decimals (Exercise 3E) | Mathematics (Maths) Class 7 PDF Download

Q.1. 0.06 = ?
(a) 3/5
(b) 3/50
(c) 3/500
(d) none of these
Ans. (b) 3/50
0.06 = 6100=3506100=350

Q.2. 1.04 = ?
(a)
(b)
(c)
(d) none of these
Ans. (c)
1.04 = 104/100 = 26/25 =

Q.3. = ?
(a) 2.8
(b) 2.08
(c) 2.008
(d) none of these
Ans. (b) 2.08
 = 52/25
On dividing, we get:

∴ 2225=52252225=5225 = 2.08

Q.4. 6 cm = ?
(a) 0.006 km
(b) 0.0006 km
(c) 0.00006 km
(d) none of these
Ans. (c) 0.00006 km
6 cm = 6/100 m = 0.06 m
0.06 m = 0.06/1000 km
= 0.00006 km
∴ 6 cm = 0.00006 km

Q.5. 70 g = ?
(a) 0.7 kg
(b) 0.07 kg
(c) 0.007 kg
(d) none of these
Ans. (b) 0.07 kg
70 g = 70/1000 kg
= 7/100 kg
= 0.07 kg
∴ 70 g = 0.07 kg

Q.6. 5 kg 6 g = ?
(a) 5.0006 kg
(b) 5.06 kg
(c) 5.006 kg
(d) 5.6 kg
Ans. (c) 5.006 kg
5 kg 6 g = (5 ×× 1000) g + 6 g = 5006 g
= 5006/1000 kg
= 5.006 kg
∴ 5 kg 6 g = 5.006 kg

Q.7. 2 km 5 m = ?
(a) 2.5 km
(b) 2.05 km
(c) 2.005 km
(d) 2.0005 km
Ans. (c) 2.005 km
2 km 5 m = (2 ×× 1000) m + 5 m = 2005 m
= 2005/1000 km = 2.005 km
∴ 2 km 5 m = 2.005 km

Q.8. (1.007 − 0.7) = ?
(a) 1
(b) 0.37
(c) 0.307
(d) none of these
Ans. (c) 0.307
Converting the given decimals into like decimals, we get:
1.007 and 0.700
Writing them in column form with the larger one at the top and subtracting, we get:

Hence, the required number is 0.307.

Q.9. What should be subtracted from .1 to get .03?
(a) .7
(b) .07
(c) .007
(d) none of these
Ans. (b) .07
We have:
0.1 − x = 0.03
⇒ x = 0.1 − 0.03
Converting the given decimals into like decimals, we get:
0.10 and 0.03
Writing them in column form with the larger one at the top and subtracting, we get:

∴ x = 0.07
Hence, the required number is 0.07.

Q.10. What should be added to 3.07 to get 3.5?
(a) .57
(b) .34
(c) .43
(d) .02
Ans. (c) .43
We have:
3.07 + x = 3.5
⇒ x = 3.5 − 3.07
Converting the given decimals into like decimals, we get:
3.07 and 3.50
Writing them in column form with the larger one at the top and subtracting, we get:

∴ x  = 0.43
Hence, 0.43 should be added to 3.07 to get 3.5.

Q.11. 0.23 × 0.3 = ?
(a) 0.69
(b) 6.9
(c) 0.069
(d) none of these
Ans. (c) 0.069
First, we will multiply 23 by 3.
i.e., 23 × 3 = 69
Sum of decimal places in the given decimals = (2 + 1) = 3
∴ 0.23 × 0.3 = 0.069 ( 3 places of decimal)

Q.12. 0.02 × 30 = ?
(a) 6
(b) 0.6
(c) 0.06
(d) none of these
Ans. (b) 0.6
We have:
2 × 30 = 60
∴ 0.02 × 30 = 0.60 (2 places of decimal)
= 0.6

Q.13. 0.25 × 0.8 = ?
(a) 0.02
(b) 0.2
(c) 0.002
(d) 2
Ans. (b) 0.2
First, we will multiply 25 by 8.
∴ 25 × 8 = 200
Sum of decimal places in the given decimals = (2 + 1) = 3
∴ 0.25 × 0.8 = 0.200 [3 places of decimal]
= 0.2

Q.14. 0.4 × 0.4 × 0.4 = ?
(a) 6.4
(b) .64
(c) .064
(d) none of these
Ans. (c) .064
First, we will find the product 4 × 4 × 4 = 64
Sum of decimal places in the given decimals = (1 + 1 + 1) = 3
∴ 0.4 × 0.4 × 0.4 = 0.064 ( 3 places of decimal)

Q.15. 1.1 × .1 ×.01 = ?
(a) .011
(b) .0011
(c) .11
(d) none of these
Ans. (b) .0011
First, we will find the product 11 × 1 × 1.
Sum of decimal places in the given decimals  = (1 + 1 + 2) = 4
∴ 1.1 ×  0.1 × 0.01 = 0.0011   (4 places of decimal)

Q.16. 2.08 ÷ (.16) = ?
(a) 13
(b) .13
(c) 1.3
(d) none of these
Ans. (a) 13
2.08 ÷ 0.16 = 2.08/0.16
= (2.08×100) / (0.16×100)
= 208/16
=132

Q.17. 1.02 ÷ 6 = ?
(a) 1.7
(b) 0.17
(c) 0.017
(d) none of these
Ans. (b) 0.17
= 1.02 ÷ 6
= 1.02/6
= (1.02×100) / (6×100)
= 102 / (6×100)
= 17/100
= 0.17

Q.18. 30.94 ÷ 0.7 = ?
(a) 44.2
(b) 4.42
(c) 442
(d) 0.442
Ans. (a) 44.2
30.94 ÷ 0.7 = 30.94/0.7
= (30.94×100) / (0.7×100)
= 3094/70
= 44.2

Q.19. 2.73 ÷ 1.3 = ?
(a) 21
(b) 2.1
(c) 0.21
(d) none of these
Ans. (b) 2.1
2.73 ÷ 1.3
= 2.73/1.3
= (2.73×100) / (1.3×100)
= 273 / (13×10)
= 21/10
= 2.1

Q.20. 89.1 ÷ 2.2 = ?
(a) 40.5
(b) 4.05
(c) 41
(d) 41.5
Ans. (a) 40.5
89.1 ÷ 2.2 = 89.1/2.2
= (89.1 × 10) / (2.2 × 10)
= 891/22
= 40.5

Q.21. 0.5 × 0.05 = ?
(a) 0.25
(b) 2.5
(c) 0.025
(d) none of these
Ans. (c) 0.025
First, we will multiply 5 by 5.
i.e., 5 × 5 = 25
Sum of decimal places in the given decimals = (1 + 2) = 3
∴ 0.5 × 0.05 = 0.025   (3 places of decimal)