Targeting Grade C GCSE Mathematics Number Unit 4 Percentages and Interest

Can you: If not you need Find percentages of amounts Find percentage increase or decrease Try a test Find simple interest Find compound interest 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 If not 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 Remember to split the amount into 10% (by dividing by 10) and then multiply by the number of 10s you need! Lesson

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 Split your percentage into parts like 10%, 5%, 2 ½% and 1% 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

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% One way to increase or decrease amounts by percentages is to find the percentage and then add (to increase) or subtract (to decrease) Lesson

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

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. Find the interest for one year then multiply by the number of years! Lesson

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. Remember the formula (1+(percentage  100))number of years to help you e.g. for (1) do £150  (1.07)2 Lesson

TAIL 2 (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. (1) 5/100  269.30 = 13.465 269.30 – 13.465 = 255.835 = £255.84 (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