Sheet № 78 · Foundation + Higher · AQA · Edexcel · OCR
Percentage to Multiplier – Quick Conversion
Percentage multipliers give you a fast, one-step way to calculate percentage increases and decreases. Instead of finding the percentage and then adding or subtracting, you multiply by a single decimal — saving time and reducing errors on both calculator and non-calculator GCSE papers.
§Key definitions
Question:
Increase £350 by 12%.
Answer:
£11,054.25
Q1 (Foundation):
Decrease £480 by 25%.
Q2 (Foundation):
A TV costs £560. The price is increased by 8%. What is the new price?
Q3 (Higher):
A painting increases in value by 6% each year. It is currently worth £1,200. What will it be worth in 5 years? Give your answer to the nearest pound.
§Formulas to memorise
Multiplier for increase = 1 + (percentage / 100)
Multiplier for decrease = 1 − (percentage / 100)
After n repeated changes: final value = original × multiplier^n
Worked example
Increase £350 by 12%.
Working:
⚠ Common mistakes
- ✗Using 0.15 instead of 1.15 for a 15% increase. Multiplying by 0.15 gives you 15% of the amount, not the amount increased by 15%. The multiplier must include the original 100%.
- ✗Applying repeated percentage change as a single large percentage. A 10% increase for 3 years is not a 30% increase. You must multiply by 1.10 three times, which gives 1.331 — a 33.1% increase.
- ✗Mixing up increase and decrease multipliers. A 20% decrease uses 0.80, not 1.20. Always check: is the multiplier making the number bigger or smaller?
✦ Exam tips
- →Write down the multiplier explicitly — examiners award a method mark for stating it correctly.
- →For repeated change problems, write the expression in full (e.g. 18000 × 0.85³) before calculating. This earns method marks even if you make an arithmetic error.
- →If a question asks you to find the original value before a percentage change, divide by the multiplier — this links to reverse percentages.