Page 106 - ICSE Math 7

8 Percentage

Key Concepts

• Percentage • Finding Percentage of a Given Quantity
• Expressing Smaller Units as Percentage of Larger Units • Finding the Number from a Given Percentage of the
• Expressing One Quantity as a Percentage of the Number
Other • Increase or Decrease in Percentage

In this chapter, we will learn about percentage and conversion of a given fraction or decimal into
percentage, and vice versa. We will also learn how to express smaller units as percentages of larger
units, how to express one quantity as a percentage of the other, how to find percentage of a given
quantity, how to find a number from a given percentage of the number and how to find increase or
decrease in percentage.

Percentage

Per cent means ‘out of hundred’ or ‘for every hundred’ and it is denoted by the symbol %. Suppose in
a committee 57 members out of 100 members are women and rest are men. We say that, 57 per cent
of members are women. Percentages are the fractions having 100 as denominators.
Example:
33
33 out of 100 = 100 = 33% (read as 33 per cent)

Conversion of a fraction or a decimal into percentage
To convert a given fraction or decimal into percentage, multiply the given fraction or decimal by 100
and put the symbol of percentage after the product. Example:
)
(a) 17 = ( 17 × 100 % = 68% (b) 0.35 = (0.35 × 100)% = 35%
25 25

Conversion of percentage into a fraction or decimal
To convert a given percentage into a fraction or decimal, remove the symbol of percentage and divide
it by 100. Example:
28 7 22.5
(a) 28% = = (b) 22.5% = = 0.225
100 25 100
Conversion of ratio into percentage
To convert ratio into percentage, first write the ratio as fraction and then multiply it by 100 and write
% symbol. Example: Each part of the ratio 1 : 2 : 5 can be converted into percentage as
Sum of the ratios = 1 + 2 + 5 = 8

1 2 5
∴ First part = × 100 % ∴ Second part = × 100 % ∴ Third part = × 100 %
8 8 8
1 1
= 12 % = 25% = 62 %
2 2

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