Page 130 - Start Up Mathematics_7

3 3 100 3
(c) = × = × 100% = 7.5%
40 40 100 40
1 1 100 1 100 2
(d) = × = × 100% = % = 14 %
7 7 100 7 7 7

Example 5: Estimate the part of the circle which is shaded and convert it into percent.

(a) (b) (c)

2
Solution: (a) part is shaded.
4
2 2 100 1
∴ = × 100 = × 100% = 50% is shaded.
2
4
4
2
(b) part is shaded.
8
2 2 100 2 200
∴ = × 100 = × 100% = 8 % = 25% is shaded.
8
8
8
3
(c) part is shaded.
8
3 3 100 3
∴ = × = × 100% = 37.5% is shaded.
8 8 100 8
Converting decimals to percentage

To convert decimals to percentage, write decimals as fractions first and then multiply by 100% or
simply multiply the decimal by 100% as shown below.

Example 6: Convert the given decimal fractions to percent.
(a) 0.65 (b) 2.1 (c) 0.02 (d) 12.35
Solution: (a) 0.65 = 0.65 × 100% = 65% (b) 2.1 = 2.1 × 100% = 210%

(c) 0.02 = 0.02 × 100% = 2% (d) 12.35 = 12.35 × 100% = 1235%

Converting percentage to fractions or decimals
To convert percentage to fraction, remove the percentage sign (%) and divide it by 100. To further
convert a fraction having denominator 100 into decimal, move the decimal point two places to
the left and remove 100.

20
It is done by writing say 20% as (fraction form) = 0.20 (decimal form).
100

Uses of Percentage
It is a very handy tool to compare quantities. It is also used to find ‘How many’. For example,
30
30% of 300 = × 300 = 90
100

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