Edexcel International GCSE Mathematics A · 4MA1
Percentage change
A percentage change compares the change in a quantity with its original value. Multipliers keep repeated changes clear and avoid confusing the starting amount with the final amount. A percentage increase followed by the same percentage decrease does not cancel.
Key method
Percentage change = (new − original)/original × 100%. For an increase of r%, multiply by 1 + r/100; for a decrease, use 1 − r/100.
Worked example
A price rises from 80 to 92. Find the percentage increase.
- Find the increase: 92 − 80 = 12.
- Compare with the original price: 12/80 = 0.15.
- Multiply by 100 to express the ratio as a percentage.
Answer and interpretation
15% increase.
Common mistake
Dividing by 92 measures the change against the final price instead of the original price.
Practise independently
A value of 200 increases by 10% then decreases by 20%. Find the final value.
Check your answer
200 × 1.10 × 0.80 = 176, an overall decrease of 12%.
Syllabus connection
This lesson develops percentage change within the number area. Start with the worked method, attempt the independent question without looking at its answer, then explain any correction in your own words. Check the official specification for your tier’s full requirements.
Related resources
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