Free Cambridge IGCSE Maths Formula Sheet
All 49 essential formulas you need for your Cambridge IGCSE maths exam, organised by topic. Enter your email to unlock the full sheet and print it as a PDF.
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Percentage of an Amount
Amount × (Percentage ÷ 100)
E.g. 15% of 80 = 80 × 0.15 = 12
Percentage Increase
New Value = Original × (1 + r⁄100)
r is the percentage increase. Multiply by the multiplier directly.
Percentage Decrease
New Value = Original × (1 − r⁄100)
r is the percentage decrease. E.g. 20% off → multiply by 0.8.
Compound Interest
A = P(1 + r⁄100)ⁿ
P = principal, r = annual rate (%), n = number of years.
Reverse Percentage
Original = Final Amount ÷ Multiplier
To find the original before a % change. E.g. after 20% increase, divide by 1.2.
Percentage Change
% Change = (Change ÷ Original) × 100
Use for both increase and decrease. Always divide by the original value.
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