What is a discount?
A discount is money taken off the price. It’s often given as a percentage (%), which means “out of 100”.
Sale price = original price − discount
Percentages you can work out in your head
| Percentage | Fraction | How to find it | Example: of £40 |
|---|---|---|---|
| 50% | ½ | ÷ 2 | £20 |
| 25% | ¼ | ÷ 4 (halve, then halve again) | £10 |
| 10% | 1⁄10 | ÷ 10 | £4 |
| 5% | 1⁄20 | half of 10% | £2 |
| 20% | 1⁄5 | 10% × 2 | £8 |
| 15% | 10% + 5% | £6 | |
| 75% | ¾ | 50% + 25% | £30 |
Worked example
A lamp costs £40. There is 15% off. What is the sale price?
- 10% of £40 = £4
- 5% of £40 = £2
- 15% = £4 + £2 = £6 off
- Sale price: £40 − £6 = £34
Special offers
Buy one, get one free: you pay for half of the items. If there’s an odd number, you pay for the extra one too.
5 T-shirts at £8, buy one get one free → pay for 3 → 3 × £8 = £24
Working backwards (the tricky one)
After 20% off, a jumper costs £24. What was the original price?
The sale price is 100% − 20% = 80% of the original. 80% = £24 → 10% = £3 → 100% = £30
Watch out! Read what the question asks: the discount (the money off) or the sale price (what you pay). The discount is the smaller number.
Top tip: check your sale price is less than the original, and makes sense. 50% off £12 can’t be £10!
Which fraction is the same amount? Tap the right box.
50%
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