% Percentages %

2. % Percentages % What does percent mean? ‘per cent’means per hundred %means /100 So 50% means 50 out of 100

3. To change a percentage to a fraction • Percentages already are fractions: always fractions of 100: • 20% means • Next step: simplify: 20 100 20 100 2 10 1 5 = =

5. 70 100 28 100 50 100 35 100 5 100 20 100 90 100 1 100 80 100 6 100 64 100 2 100 22 100 15 100 4 100

6. 7 10 7 25 1 2 7 20 1 20 1 5 9 10 1 100 4 5 3 50 16 25 1 50 11 50 3 20 1 25

8. 25% 8% 16% 10% 85% 98% 30% 75% 96% 34% 40% 60% 45% 95% 18%

9. You have 1p, 5p, 10p and 50p coins. What is the smallest number of these coins you need to make: 28p 37p 73p 46p 17p 62p 99p

10. How to find a % of an amount If it’s a simple percentage, use the fraction equivalent (eg for 50%, 25%, 10% use ½, ¼, 1/10) If it’s a combination of simple ones, work them out, then put them together (eg for 75% do 3 x 25%, or for 30% do 3 x 10%) If it’s more complex, split it into simple ones. (eg 37% = 3 x 10% + 7 x 1%)

11. 26% of £50 = 10% of £50 + 10% of £50 + 5% of £50 + 1% of £50 = £5 = £5 = £2.50 = £0.50 = £13

12. Finding a percentage change – Method 1 To calculate a change in percentage, first work out the percentage change as an amount, then add it on (or take it off). Adding on 25% of 800ml which is 200ml RoundUp: Usually 800ml New Amount: 1000ml (or 1l)

13. Finding a percentage change – Method 2 Write the final percentage as a decimal (eg for a 25% increase, 1.25, or a 30% decrease, 0.7), then multiply by the original amount. 15% decrease leaves 85% or 0.85, so x 0.85 Drill: Usually £180 New Price: £153

14. £16 £50 £68 £150 £300 1 2 3 4 5 £12 £37.50 £51 £112.50 £225

15. £62,000 £87 £93.50 £16.29 £96 1 2 3 4 5 £55,800 £78.30 £84.15 £14.66 (rounded down) £86.40

16. £62 £1000 £1.00 £12 £600 1 2 3 4 5 £49.60 £800 £0.80 £9.60 £480

17. 84 96 48 56 50 1 2 3 4 5 126 144 72 84 75