Example 1
Find 10% of £80.00.
- 10% means one tenth of the amount.
- Divide 80 by 10.
- 80 divided by 10 = 8
So: 10% of £80.00 is £8.00.
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Topic
Percentages
Percentages are used for discounts, tax, interest, results, and comparing changes. A percentage means out of 100, so 40% means 40 out of every 100.
Topic explanation
To find a percentage of an amount, change the percentage into a decimal, then multiply. For example, 15% is 0.15, so 15% of £80 is 0.15 × 80 = £12.
For percentage change, compare the change with the original amount. Use: percentage change = change divided by original × 100.
For reverse percentages, work backwards from the final amount. If an amount has been increased by 30%, the final amount is 130% of the original, so divide by 1.30.
Quick methods
- 10%
- Divide by 10.
- 5%
- Find 10%, then halve it.
- 25%
- Divide by 4.
- Increase by 20%
- Multiply by 1.20.
- Decrease by 20%
- Multiply by 0.80.
Worked examples
Example 2
A jacket costs £45.00. It has 20% off. What is the sale price?
- First find 10% of £45.00: 45 divided by 10 = £4.50
- 20% is double 10%, so £4.50 × 2 = £9.00
- Take the discount away: £45.00 − £9.00 = £36.00
So: The sale price is £36.00.
Example 3
A price is increased by 15% to £92.00. What was the original price?
- After a 15% increase, the new price is 115% of the original.
- Write 115% as 1.15.
- Divide the new price by 1.15: 92 divided by 1.15 = 80
So: The original price was £80.00.