OCR GCSE MATHS 13.3 PERCENTAGE CHANGE EXAM

13.3 Percentage change ©Cambridge University Press and OCR 2020 1 13 Percentages 13.3 Percentage change • increasing and decreasing amounts by a given percentage • finding original values • finding percentage change. Increasing and decreasing amounts by a given percentage WORKED EXAMPLE Increase 50 by 8%. Solution Method 1 First find 8% of 50. The increase is 4. The increased value is 50 + 4 = 54. The answer is 54. Method 2 Original value = 100% Increase = 8% New value = 100 + 8 = 108% The increased value is 50 × 1.08 = 54. The answer is 54. TIP To increase a number by x%, multiply the original value by . So, to increase by 25%, multiply by 1.25 (since 1 + = 1 + 0.25 = 1.25). To decrease a number by x%, multiply the original value by . So, to decrease by 25%, multiply by 0.75 (since 1 − = 1 − 0.25 = 0.75).