A percentage change is a way of expressing an increase, or decrease, in an amount (usually money) relative to the original amount.
For example, if the price of a TV increases from £400 to £450, the price has increased by £50, but expressed as a percentage of the original price, this would be 12.5%.
In GCSE Mathematics, you may be asked to find a new amount after a given percentage increase or decrease; alternatively you may be asked to find the percentage increase or decrease, given the 'before' and 'after' amounts.
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