Using percentages for discount calculations
Sometimes shops offer discounts in the form of a percentage.
If the shop is offering 25% discount then we would work out 25% of the original price.
We would then subtract the answer from the original price to get the new price.
Example
A shop is offering 30% discount on all goods. Howe much would you pay for an item normally priced at £140?
Answer
- 1% of £140 = £1.40
- 30% = 30 x £1.40 = £42
- £140 - £42 = £98
The new price is £98.
Question
Dylan’s Deli reduces their sandwiches by 30% at 3pm. Calculate the cost of these sandwiches after 3pm:
- A ham sandwich, which originally cost £2.50.
- A falafel sandwich, which originally cost £4.
- Ham sandwich
- 1% of £2.50 = 2.5p
- 30% = 30 x 2.5p = 75p
- £2.50 - £0.75 = £1.75
- The discounted ham sandwich costs £1.75
- Falafel sandwich
- 1% of £4 = 4p
- 30% = 30 x 4p = £1.20
- £4 - £1.20 = £2.80
- The discounted falafel sandwich costs £2.80.
You may notice that the falafel sandwich has a bigger discount. This is because the original price was higher.
Alternative method
There is an alternative way of calculating this. Sandwich prices are reduced by 30% which means that the reduced price is 70% of the original price.
Question
Can you work out 70% of the sandwich prices directly without calculating 30% first?
- A tuna sandwich which originally cost £3.00
- A carrot and humous sandwich which originally cost £2.00
- Tuna sandwich
- 70% of £3.00 = £3.00 ÷ 100 × 70 = £2.10
- The discounted tuna sandwich costs £2.10
- Carrot and humous sandwich
- 70% of £2.40 = £2.40 ÷ 100 × 70 = £1.68
- The discounted carrot and humous sandwich costs £1.68.
