220 Appendix G
If you read that 23% of people have blond hair, it means that 23
people out of every 100 have blond hair. You could also say that
0.23 of the population has blond hair, but it is easier and more
common to say it as a percentage.
Money has built-in percentages. Because there are 100 cents in a
dollar, 54 cents is 54% of a dollar.
CALCULATING A QUANTITY
AS A PERCENTAGE OF ANOTHER
How do you fi nd what percentage one number is of another? For
instance, if 32 people at a meeting are females and there are 58
people attending, what percentage are female? As a fraction they are
⁄. To fi nd the percentage you simply multiply this by 100.
You calculate this as follows:
32 / 58 × 100 = 3,200/ 58 %
3,200 ÷ 58 = 55^10 / 58 %
Th is would normally be expressed as a decimal: 55.17%.
So, 25 boys in a crowd of 50 would mean that 50% are boys. Why?
Because half are boys and ½ times 100 is 50. We simply multiply
the fraction by 100.
On the other hand, to fi nd a percentage of a number—for instance,
what is 20% of 2,500—we multiply the number by the percentage
divided by 100. We would set it out like this:
2,500 ×^20 / 100 =
We can cancel the one hundreds, or simply divide 2,500 by 100,
which is, of course, 25. Th en multiply 25 by 20 (multiply by 2, then
by 10) to get 500.
2,500 ×^20 / 100 = 25 × 20 = 500
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