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Percentages and percentage change
Percentages are everywhere: discounts, pay rises and test scores. A multiplier makes every question quicker.
Percentage of an amount
Find 10% by dividing by 10, 1% by dividing by 100, then build up.
Or use a decimal: 35% of 80 = 0.35 × 80 = 28.
Or use a decimal: 35% of 80 = 0.35 × 80 = 28.
Multipliers
Increase by 15%: multiply by 1.15. Decrease by 15%: multiply by 0.85.
A £60 jacket with 20% off: 60 × 0.8 = £48.
A £60 jacket with 20% off: 60 × 0.8 = £48.
Percentage change
percentage change = changeoriginal × 100
From 50 to 65: 1550 × 100 = 30% increase.
One number as a percentage of another: 1824 × 100 = 75%.
From 50 to 65: 1550 × 100 = 30% increase.
One number as a percentage of another: 1824 × 100 = 75%.
A price rises from £40 to £46. Find the percentage increase.
- Change = £6
- 640 × 100
- = 15%
Answer: 15%
Use multipliers: 1 + r for an increase, 1 − r for a decrease. Percentage change = change ÷ original × 100.
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