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Year 7 · Fractions and percentages of amounts

Find a fraction of an amount

Definition

Per cent means "out of 100". A percentage is just a fraction with a denominator of 100, so 60% means 60 out of every 100, or 60100, or 0.6.

Percentages compare amounts out of 100, so they make things easy to judge. Sales, test scores and phone batteries all speak in percent.

1. To find 10%, divide by 10; to find 1%, divide by 100, then build other percentages from these.
2. Percent, fraction and decimal are interchangeable: 25% = 14 = 0.25.
3. A percentage on its own is meaningless, always "percent of" something.

•A percentage increase then the same percentage decrease does not return to the start.
•50% off then 50% off is not 100% off, each cut is of a smaller amount.
•To increase by 15%, multiply by 1.15; to decrease by 15%, multiply by 0.85.

Per cent

Out of one hundred. 25 per cent means 25 out of 100, or 25100.

25 per cent is the same as 25100.