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Targeting Grade C

GCSE Mathematics. Targeting Grade C. Number Unit 4 Percentages and Interest. If not you need. Can you: Find percentages of amounts Find percentage increase or decrease Try a test Find simple interest Find compound interest Try a test.

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Targeting Grade C

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  1. GCSE Mathematics Targeting Grade C Number Unit 4 Percentages and Interest

  2. If not you need • Can you: • Find percentages of amounts • Find percentage increase or decrease • Try a test • Find simple interest • Find compound interest • Try a test TOP: Review how to find simple percentages Practice 1: Splitting percentages up Practice 2: Finding percentage increase and decrease TAIL 1 Practice 3: Finding simple interest Practice 4: Finding compound interest TAIL 2

  3. Remember to split the amount into 10% (by dividing by 10) and then multiply by the number of 10s you need! TOP:Solve these simple percentage questions. • Find 10% of £20 • Find 50% of £100 • Find 30% of £60 • Find 70% of £120 • Find 75% of £200 Lesson

  4. Split your percentage into parts like 10%, 5%, 2 ½% and 1% Practice 1:Solve these percentage problems. • Find 35% of £120 • Find 83% of £250 • Find 12% of 75kg • Find 17 ½% of 70 miles • Find 24% of £65.50 Remember to find 10%, then 1% (by dividing your 10% by 10), or 5% (by dividing your 10% by 2), or ½% (by dividing your 1% by 2), or 2 ½% (by dividing 5% by 2. Lesson

  5. One way to increase or decrease amounts by percentages is to find the percentage and then add (to increase) or subtract (to decrease) Practice 2:Find these percentage increases. • Increase £100 by 15% • Increase 85kg by 12 ½% • Increase 754 m by 68% Find these percentage decreases. • Decrease £100 by 75% • Decrease 65 miles by 34% • Decrease 378 km by 7 ½% Lesson

  6. TAIL 1 Are you ready for the answers ? • The selling price of a computer is the list price plus VAT at 17 ½ %. The list price of a computer is £786. • Work out the selling price of the computer. (1) 17 ½ /100  786 = 137.55 137.55 + 786 = £923.55 (2) 60/100  5300 = £3180 (2) Work out 60% of 5300 kg. (3) Frances sees three different advertisements for jeans. Bob’s – 15% off £30 Disco’s – ⅔ of £36 Sanjay’s – £22 + 17 ½% VAT Work out the cost of the jeans in each advertisement. (a) Bob's (b) Disco's (c) Sanjay's (3) (a) 15/100  30 = £4.50 30 – 4.50 = 25.50 (b) 2/3  36 = £24 (c) 17.5/100  22 + 22 = £25.80 Lesson

  7. Find the interest for one year then multiply by the number of years! Practice 3: Find the simple interest for the following: • £60 for 2 years at 4% interest per annum • £150 for 3 years at 7.5% interest per annum • £5000 for 6 years at 3% p.a. • £2500 for 10 years at 12.5% p.a. • £750 for 5 years at 6.5% p.a. Lesson

  8. Remember the formula (1+(percentage  100))number of yearsto help you e.g. for (1) do £150  (1.07)2 Practice 4: Find the compound interest for the following: • £150 for 2 years at 7% p.a. • £500 for 3 years at 12% p.a. • £7500 for 3 years at 3.5% p.a. • £65 for 2 years at 5% p.a. • £2500 for 4 years at 6.5% p.a. Lesson

  9. TAIL 2 (1) 5/100  269.30 = 13.465 269.30 – 13.465 = 255.835 = £255.84 (1) Yesterday Simon repaired a computer and charged a total of £269.30. Simon reduces his charges by 5% when he is paid promptly. He was paid promptly for yesterday's work on the computer. Work out how much he was paid. (2) Jane is going to buy a computer for £480 + 17 ½ % VAT. Work out the total price, including VAT, that Jane will pay for the computer. (3) Find the simple interest on £2500 invested for 2 years at 6% per year. (4) £5000 is invested for 3 years at 4% per annum compound interest. Work out the total interest earned over the three years. • Work out the simple interest on £530 at 4.5% per annum after 3 years. (2) 17 ½ /100  480 + 480 = 84 + 480 = £564 (3) 6/100  2500 = 150 “150”  2 = £300 (4) 1.043 5000 = £5624.32 (5) 4.5/100  530 = 23.85 “23.85”  3 = £71.55 Are you ready for the answers ? Lesson

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