GCSE MATHS
Percentages: of, increase, decrease and reverse
Every type of GCSE percentage question with multipliers.
Percentage of an amount
Divide by 100 and multiply by the percentage. 15% of 80 = 80 ÷ 100 × 15 = 12.
Increase and decrease with multipliers
To increase by 20%, multiply by 1.20. To decrease by 20%, multiply by 0.80. This is the quickest method in a calculator exam.
Reverse percentages
If a price after a 20% increase is £60, the original is 60 ÷ 1.20 = £50. Divide by the multiplier, never take 20% off the new price.
✏️ Worked example
A £250 jacket is reduced by 30%. What is the sale price?
Multiplier = 1 − 0.30 = 0.70. 250 × 0.70 = £175.
🧠 Test yourself
Increase £40 by 15%.
40 × 1.15 = £46.
What is 35% of 200?
70.
After a 10% discount a game costs £36. Original price?
36 ÷ 0.9 = £40.
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