Using %s (I) NON-CALCULATOR Many % s can be found without a calculator if we remember the following simple connections. (1) 50% = ½. (2) 25% = ¼. (3) 10% = 1 / 10 (4) 1% = 1 / 100

Ex1To find 15% of 160kg ……… 10% of 160kg = 16kg 5% of 160kg = 8kg So 15% of 160kg = 24kg Ex2 To find 55% of £4200 ……… 50% of £4200 = £2100 5% of £4200 = £210 So 55% of £4200 = £2310

Ex3To find 37 1 / 2 % of 160kg ……… 25% of 160kg = 40kg 12 1 / 2 % of 160kg = 20kg So 37 1 / 2 % of 160kg = 60kg Ex4 To find 3 1 / 2 % of £4200 ……… 1% of £4200 = £42 3% of £4200 = £126 1 / 2 % of £4200 = £21 So 3 1 / 2 % of £4200 = £147

Exercise (1) 17 1 / 2 % of £64 …. 10% of £64 =£6.40 5% of £64 = £ / 2 % of £64 =£1.60 So 17 1 / 2 % of £64 =£11.20 (2) 62 1 / 2 % of £56.80 ….50% of £56.80 =£ % of £56.80 = £ / 2 % of £56.80 =£7.10 So 62 1 / 2 % of £56.80 =£35.50

Percentages & Decimals USING A CALCULATOR Simple Rule - Must be Learned 23% = 0.23,77% = 0.77,6% = 0.06, NB: 60% = 0.60 or 0.6 Conversely 0.78 = 78%,0.41 = 41%,0.07 = 7%,0.025 = 2.5%

Example 34% of £45.50 =0.34 X £45.50 =£15.47 Example A bank pays interest of 3.7% per annum (yearly). Find the interest paid on £1290. Interest = 3.7% of £1290 =0.037 X £1290 = £47.73

% Reductions Example In a sale a TV set that normally costs £380 is reduced by 35%. Find the sale price. Long Method Saving = 35% of £380 = 0.35 X £380 =£133 Sale price = £380 - £133 =£247 Short Method (by multiplier) NB: removing 35% leaves 65% or 0.65 Sale price = 0.65 X £380 =£247

Timed Questions Copy & complete the following Ex1 Hi-fi - usual price £650 - Saving = 30% % paid =70% Cost = 70% of £650= 0.7 X £650= £455 Ex2 Sofa - usual price £ Saving 42% % paid = 58% Cost = 58% of £1200 = 0.58 X £1200 = £696

Exercise Now try the following setting out the answers the same way. (1) DVD Player: usual price = £280 Saving = 22% (2) Bed: usual price = £475 Saving = 34% (3) Wig: usual price £160 Saving 19% % paid =78% Cost = 78% of £280 = 0.78 X £280 = £ % paid = 66% Cost = 66% of £475 = 0.66 X £475 = £ % paid = 81% Cost = 81% of £160 = 0.81 X £160 = £129.60

Exercise Now try the following setting out the answers the same way. (4) CD Player: usual price = £190 Saving = 32% (5) Fridge: usual price = £470 Saving = 18% (6) Cinema ticket: usual price £4.80 Saving 20% % paid =68% Cost = 68% of £190 = 0.68 X £190 = £ % paid = 82% Cost = 82% of £470 = 0.82 X £470 = £ % paid = 80% Cost = 80% of £4.80 = 0.80 X £4.80 = £3.84

(7) Jeans: usual price = £37.50 Saving = 28% (8) Calculator: usual price = £8.95 Saving = 31% (9) Fish Supper: usual price £4.35 Saving 44% % paid =72% Cost = 72% of £37.50 = 0.72 X £37.50 = £27 % paid = 69% Cost = 69% of £8.95 = 0.69 X £8.95 = £6.18 % paid = 56% Cost = 56% of £4.35 = 0.56 X £4.35 = £2.44

Important Point Increasing a quantity by 12% gives us 112% of what we had already, Increasing a quantity by 8% gives us 108% of what we had already, and 112% = and 108% = This can now be used as follows …..

% Increasess Example A waitress earns £4.20 an hour but gets a 5% pay rise. Find her new pay rate. Long Method Rise = 5% of £4.20 = 0.05 X £4.20 =£0.21 New rate = £ £0.21 =£4.41 Short Method (by multiplier) NB: adding 5% gives 105% or 1.05 New rate = 1.05 X £4.20 =£4.41

Timed Questions Copy & complete the following Ex1 Joiner - usual rate £9.50 per hour - Increase = 12% New % =112% New rate = 112% of £9.50= 1.12 X £9.50= £10.64 Ex2 Town population = Increase 43% New % = 143% New population = 143% of = 1.43 X = 17160