Selina Concise Class 7 Math Chapter 4 Decimal Fractions Exercise 4C Solution
EXERCISE 4C
(1) Multiply:
(i) 0.87 × 10 = 8.7
(ii) 2.948 × 100 = 294.8
(iii) 6.4 × 1000 = 6400
(iv) 5.8 × 4 = 23.2
(v) 16.32 × 28 = 456.96
(vi) 5.037 × 8 = 40.296
(vii) 4.6 × 2.1 = 9.66
(viii) 0.568 × 6.4 = 3.6352
(2) Multiply each number by 10, 100 and 1000:
(i) 0.5 × 10 = 5; 0.5 × 100 = 50; 0.5 × 1000 = 500
(ii) 0.112 × 10 = 1.12; 0.112 × 100 = 11.2; 0.112 × 1000 = 112
(iii) 4.8 × 10 = 48; 4.8 × 100 = 480; 4.8 × 1000 = 4800
(iv) 0.0359 × 10 = 0.359; 0.0359 × 100 = 3.59; 0.0359 × 1000 = 35.9
(v) 16.27 × 10 = 162.7; 16.27 × 100 = 1627; 16.27 × 1000 = 16270
(vi) 234.8 × 10 = 2348; 234.8 × 100 = 23480; 234.8 × 1000 = 234800
(3) Evaluate:
(4) Divide:
(i) 54.9 ÷ 10 = 5.49
(ii) 7.8 ÷ 100 = 0.078
(iii) 324.76 ÷ 1000 = 0.32476
(iv) 12.8 ÷ 4 = 3.2
(v) 27.918 ÷ 9 = 3.102
(vi) 4.672 ÷ 8 = 0.584
(vii) 4.32 ÷ 1.2 = 3.6
(viii) 7.644 ÷ 1.4 = 5.46
(ix) 4.8432 ÷ 0.08 = 60.54
(5) Divide each of the given numbers by 10, 100, 1000 and 10000:
(i) 2.1 ÷ 10 = 0.21
(2.1 ÷ 100) = 0.021
(2.1 ÷ 1000) = 0.0021
(2.1 ÷ 100000) = 0.00021
(ii) 8.64 ÷ 10 = 0.864
(8.64 ÷ 100) = 0.0864
(8.64 ÷ 1000) = 0.00864
(8.64 ÷ 10000) = 0.000864
(iii) 5.01 ÷ 10 = 0.501
(5.01 ÷ 100) = 0.0501
(5.01 ÷ 1000) = 0.00501
(5.01 ÷ 10000) = 0.000501
(iv) 0.0906 ÷ 10 = 0.00906
(0.0906 ÷ 100) = 0.000906
(0.0906 ÷ 1000) = 0.0000906
(0.0906 ÷ 10000) = 0.00000906
(v) 0.125 ÷ 10 = 0.0125
(0.125 ÷ 100) = 0.00125
(0.125 ÷ 1000) = 0.000125
(0.125 ÷ 10000) = 0.0000125
(vi) 111.11 ÷ 10 = 11.111
(111.11 ÷ 100) = 1.1111
(111.11 ÷ 1000) = 0.11111
(111.11 ÷ 10000) = 0.011111
(6) Evaluate:
(i) 9.75 ÷ 5 = 1.95
(ii) 4.4064 ÷ 4 = 1.1016
(iii) 27.69 ÷ 30 = 0.923
(iv) 19.25 ÷ 25 = 0.77
(v) 20.64 ÷ 16 = 1.29
(vi) 3.204 ÷ 9 = 0.356
(vii) 0.125 ÷ 25 = 0.005
(viii) 0.14616 ÷ 72 = 0.00203
(ix) 0.6227 ÷ 1300 = 0.000479
(x) 257.894 ÷ 0.169 = 1526
(xi) 6.3 ÷ (0.3)2
= 6.3 ÷ 0.09
= 70
(7) Evaluate:
(i) 4.3 × 0.52 × 0.3
= 4.3 × 0.156
= 0.6708
(ii) 3.2 × 2.5 × 0.7
= 3.2 × 1.75
= 5.6
(iii) 0.8 × 1.5 × 0.6
= 0.8 × 0.9
= 0.72
(iv) 0.3 × 0.3 × 0.3
= 0.3 × 0.09
= 0.027
(v) 1.2 × 1.2 × 0.4
= 1.2 × 0.48
= 0.576
(vi) 0.4 × 0.04 × 0.004
= 0.4 × 0.00016
= 0.000064
(vii) 0.5 × 0.6 × 0.7
= 0.5 × 0.42
= 2.1
(viii) 0.5 × 0.06 × 0.007
= 0.5 × 0.00042
= 0.00021
(8) Evaluate:
(i) (0.9)2
= 0.9 × 0.9
= 0.81
(ii) (0.6)2 × 0.5
= 0.36 × 0.5
= 0.180
(iii) 0.3 × (0.5)2
= 0.3 × 0.25
= 0.075
(iv) (0.4)3
= 0.4 × 0.4 × 0.4
= 0.4 × 0.16
= 0.64
(v) (0.2)3 × 5
= 0.2 × 0.2 × 0.2 × 5
= 0.4 × 0.2 × 5
= 0.8 × 5
= 4
(vi) (0.2)3 × 0.05
= 0.2 × 0.2 × 0.2 × 0.05
= 0.4 × 0.2 × 0.05
= 0.8 × 0.05
= 0.04
(9) Cost of 1 kg wheat = Rs 12.80
∴ Cost of 31.50 kg wheat = Rs (31.50 × 12.80) = Rs 403.20
(10) Cost of 16 pens = Rs (56.15 × 16) = Rs 898.40
(11) Evaluate:
(i) 0.0072 ÷ 0.06 = 0.12
(ii) 0.621 ÷ 0.3 = 2.07
(iii) 0.0532 ÷ 0.005 = 10.64
(iv) 0.01162 ÷ 0.14 = 0.083
(v) (7.5 × 40.4) ÷ 25
= 303 ÷ 25
= 12.12
(vi) 2.1 ÷ (0.1 × 0.1)
= 2.1 ÷ 0.01
= 210
(12) Weight of each article = (31.50 ÷ 15) kg = 2.1 kg
(13) Cost of each article = Rs (45.96 ÷ 12) = Rs 3.83
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