Page 107 - ICSE Math 7

Conversion of percentage into a ratio
To convert a percentage into ratio, first convert percentage into fraction in the simplest form and then
write it as ratio. Example:
9
20 1 2.25 225 9
(a) 20% = = (b) 2.25% = = =
100 5 100 100 × 100 400
4
∴ Required ratio = 1 : 5 ∴ Required ratio = 9 : 400

Example 1: Express the following as percentages.
4 1
(a) (b) 4 (c) 2.5 (d) 11 : 25
5 4
4 4 1 17
Solution: (a) = × 100 % = (4 × 20)% = 80% (b) 4 = × 100 % = (17 × 25)% = 425%
5 5 4 4

11
(c) 2.5 = (2.5 × 100)% = 250 (d) 11 : 25 = × 100 % = 44%
25
Example 2: Express 35% as a fraction, decimal and ratio.
35 7
Solution: 35% = =
100 20
35 35 7
Also, 35% = = 0.35 and 35% = = = 7 : 20
100 100 20

Expressing Smaller Units as Percentage of Larger Units
Rupee and paise Try This

100 paise = 1 rupee Complete the following.
1
∴ 1 paise = rupee = 1% of a rupee (a) 20 paise = ____% of a rupee
100 (b) 18 cm = ____% of 1 m
Similarly, 2 paise = 2% of a rupee (c) 458 g = ____% of 1 kg
(d) 162 mL = ____% of 1 L
Metres and centimetres

100 cm = 1 m
1
∴ 1 cm = m = 1% of 1 metre
100
Similarly, 2 cm = 2% of 1 metre
Kilograms and grams

1,000 g = 1 kg
1 1 1 0.1
∴ 1 g = kg = × of 1 kg = of 1 kg = 0.1% of 1 kg
1000 10 100 100
Similarly, 2 g = 0.2% of 1 kg and 35 g = 3.5% of 1 kg

Litres and millilitres
1,000 mL = 1 L
1 1 1 0.1
∴ 1 mL = L = × of 1 L = of 1 L = 0.1% of 1 L
1000 10 100 100
Similarly, 2 mL = 0.2% of 1 L and 17 mL = 1.7% of 1 L
While expressing one quantity as a percentage of the other, both the quantities should be in same units.

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