How to see it
Percentages of an amount: find ten per cent by dividing by ten, then build up. Increase and decrease: add or take away. Backwards: the new price is more than the old one, 120 per cent of it. So divide by 1.2.
A worked example
15 per cent of 240. Ten per cent is 24. Five per cent is 12. Together, 36. Now the coat. 96 is 120 per cent. So 1 per cent is 0.8, and 100 per cent is £80.
The common mistake: taking the percentage off the new price when going backwards
The trap is taking 20 per cent off the £96. That gives £76.80. But the 20 per cent was of the original price, not the new one.
Try one
After a 10 per cent increase, a bike costs £66. What was the price before?
- A£59.40
- B£56
- C£60
- D£72.60
Show the answerHide the answer
Right: C, £60
£66 is 110 per cent, so divide by 1.1.