Percentage
What fraction of a whole a part represents, out of 100.
Formula
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Example
15 out of 60 = 25%
How it works
A percentage tells you how many parts out of 100 a quantity represents. The formula works by first finding the fraction of the whole, then scaling that fraction to an equivalent value out of 100 by multiplying by 100. For example, if something is half of the whole, the fraction is 1/2 and multiplying by 100 gives 50%.
When to use it
Use this formula when you want to express a part of a total as a percent, such as test scores, discounts, survey results, or how much of a container has been filled. It is also useful when comparing different quantities on the same 100-point scale.
Worked example, step by step
Find the percentage if the part is 18 and the whole is 72. % = (part / whole) × 100 % = (18 / 72) × 100 % = 0.25 × 100 % = 25% Final answer: 25%
Common mistakes to avoid
- Swapping the part and whole in the fraction
- Forgetting to multiply by 100 at the end
- Using units in the final percent answer instead of just %
Did You Know?
The word "percent" comes from the Latin "per centum", meaning "by the hundred" — the % sign evolved from a shorthand scribbles of "cto".
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