GCSE MATHS • HIGHER TIER

Percentage of an Amount Made Simple

Find percentages quickly using formulas, mental methods and fraction equivalents.

Clear method

Exam practice

Worked proofs

Percentage of an Amount in Four Moves

1 Identify

Identify the percentage and the amount .

2 Choose

Choose the formula, a mental percentage method or a fraction equivalent .

3 Calculate

Work out the required percentage of the amount .

4 Check

Check that your answer is sensible for the percentage given .

What You’ll Learn

Understand what a percentage means.

Use the percentage-of-an-amount formula.

Find 10%, 5% and 1% mentally.

Use fractions for familiar percentages.

Calculate percentages of money and discounts.

Choose an efficient method in GCSE questions.

Key Rules

Percentage means “out of 100”.

Use the formula:

Percentage of an amount = (Percentage ÷ 100) × Amount.

Convert the percentage to a decimal before multiplying.

Example : 20% = 0.20

Use fraction equivalents for common percentages :

50% = ½, 25% = ¼ and 75% = ¾

Worked Proof: Percentage of an Amount

Step-by-Step Method

More Worked Examples

1

Find 20% of 50

20 ÷ 100 = 0.2

0.2 × 50 = 10

Answer = 10

2

Find 15% of £200

10% = £20

5% = £10
15% = £30

Answer = £30

3

Find 18% of £350

18% = 18 ÷ 100 = 0.18

£350 × 0.18 = £63

Answer = £63

4

Find 32% of £250

32% = 32 ÷ 100 = 0.32

£250 × 0.32 = £80

Answer = £80

Choose the quickest reliable method for the percentage given.
Use the formula method for awkward percentages or calculator questions.
Use 10%, 5% and 1% to build percentages mentally.
Use fraction equivalents for familiar percentages such as 25%, 50% and 75%.
For discounts, calculate the discount first and then subtract it from the original price.
Check whether your answer is reasonable compared with the original amount.