Percentage change
Sometimes prices, volumes and other quantities are increased or decreased by a percentage of the original amount. It is useful to be able to calculate the percentage change and the new amount.
One straightforward way to do this is in three steps.
Increasing or decreasing by a given percentage
- Calculate one percent
- Calculate the percentage given
- Add or subtract the percentage as required
Example
A landlord raises his rental prices by 5%. How much will rent priced at £350 a month cost after the increase?
Answer
- 1% of £350 = £3.50
- 5% = 5 x £3.50 = £17.50 (this is the amount of increase)
- £350 + £17.50 = £367.50
The new rent is £367.50 per month.
Question
A shop reduces all their stock by 15%. How much would a jacket, costing £60, now cost in the sale?
- 1% of £60 = £0.60
- 15% = 15 x £0.60 = £9 (this is the amount of decrease)
- £60 - £9 = £51
The sale price of the jacket is £51.