6.1 Percentage of an amount — Learn

Prerequisites: equivalent fractions and decimal multiplication.

Objectives: find a percentage of an amount using a fraction, decimal or known percentage.

A percentage means “out of 100”. So 1% is one hundredth of an amount. Divide by 100 to find 1%, then multiply by the required number of percent.

Example 1. Work out 35% of £240.

10% of £240 is £24.

30% is $3 × £24 = £72$.

5% is half of 10%, so it is £12.

35% is $£72 + £12 = £84$.

Example 2. Work out 18% of 350 using a decimal multiplier.

18% = 0.18.

0.18 × 350 = 63.

Watch out. Multiplying by 35 gives 35 times the amount, not 35% of it. Convert 35% to 0.35, or split it into known percentages. Check that 35% of a positive amount is less than that amount.

Progress check

A savings account has £600. Predict 4% of £600 before moving on. The exact amount will help you calculate interest later.

You should now be able to

• explain that a percentage is a number of parts per hundred;
• find a percentage using known percentages or a decimal multiplier;
• check whether an answer is a sensible part of the original amount.