Page 84 - ICSE Math 8

7 Percentage

Key Concepts

• Converting a Fraction or a Decimal to Percentage and • Finding the Number from a Given Percentage of the
Vice Versa Number
• Expressing One Quantity as a Percentage of the Other • Increase or Decrease in Percentage
• Finding Percentage of a Given Quantity

We use percentages in our day-to-day life. Shops give discounts as percentages, banks charge interest on
loans as percentage, or pay interest for money invested as percentage, your overall academic performance is
calculated as a percentage, and so on.
Per cent means ‘for every hundred’. It is denoted by the symbol ‘%’. Percentages are fractions having 100 as
their denominator. The numerator in such fractions can be written as a per cent with a symbol of % added to it.
For example, 57 out of 100 = 57 = 57% (read as 57 per cent). In this chapter, we will learn to convert fractions
100
or decimals into percentages and vice versa.

Converting a Fraction or a Decimal to Percentage
To convert a given fraction or decimal to percentage, multiply the given fraction or decimal by 100 and put
the per cent symbol. For example,

(a) 6 =   6 × 100 % = 40% (b) 0.36 = (0.36 × 100)% = 36%

15  15 
Converting a Percentage to a Fraction or a Decimal

To convert a given percentage to a fraction or a decimal, remove the per cent symbol of the fraction and divide
it by 100. For example,
64.5 129 37
(a) 64.5% = = (b) 37% = = 0.37
100 200 100
Expressing One Quantity as a Percentage of the Other
To express a quantity as a percentage of the other quantity of the same kind, divide the first quantity by the
second and then multiply by 100%. For example,
24
(a) ` 24 as the per cent of ` 192 = × 100% = 12.5%
192
0.1  100 
(b) 100 mL as the per cent of 25 L = × 100% = 0.4% 100mL = L

25  1 000 
,

Finding Percentage of a Given Quantity
Express the given per cent as a fraction of 100 and multiply by the given number. For example,
15% of ` 7,500 = 15 × ` 7,500 = ` 1,125
100
Example 1: What per cent of 0.50 quintal is 2 kg 450 g?
Solution: 2 kg 450 g = 2,450 g and 0.50 quintal = 0.50 × 1,00,000 g = 50,000 g

2,450
Required percentage = 50,000 × 100% = 4.9%

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