# Percentage of an amount

A percentage means 'out of 100'. To find a percentage of an amount, break it into easy chunks like 10% and 1%.

Maths (school) · Part 01: Number and ratio · Card 3 of 9 · Last updated 2026-10-19

## Analogy

Like splitting a bill: find one tenth first, then build up from there.

## Example

**15% of 80**

10% of 80 = 8
5% of 80 = 4
15% of 80 = 8 + 4 = 12

## In practice

Shops use it for sales: 20% off a 50 pound coat takes 10 pounds off.

## Practice

### Flashcards

- **What is 15% of 80?** 12. It is 10% (8) plus 5% (4).

## Questions people ask

### How do you find 10% of a number quickly?

Divide the number by 10. Ten percent is one tenth. So 10% of 80 is 8, and 10% of 250 is 25. You can then double it for 20%, halve it for 5%, or add chunks together to build other percentages.

### How do you turn a percentage into a decimal?

Divide by 100, which moves the decimal point two places left. So 35% becomes 0.35 and 7% becomes 0.07. To find 35% of 60, multiply 0.35 x 60 = 21. This is the method a calculator needs. Many calculators have a percent key too, but the divide-by-100 method always works.

## Related concepts

- [Percentage change](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-4)
- [BIDMAS](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-1)
- [Adding fractions](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-2)
- [Laws of indices](https://studyvisually.com/learn/science/maths-school/maths-school-part-1/maths-school-part-1-concept-7)

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