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