Maths Revision Lesson 1 4.0 / 5 based on 1 rating ? MathematicsOtherAll boards Created by: NiamhCreated on: 13-05-10 17:43 Question Percentage Change Using A Multiplying Factor A multiplying factor is a decimal which is equivalent to the percentage that you want to add up with. Find 89% of £46.20 1 of 14 Answer 89% divided by 100 = 0.89 0.89 x 46.20= £41.118 2 of 14 Question Simple Interest This is when the interest is calculated at the beginning of the investment and the amount added each year is the same. £450 is deposited in a simple interest account which earns interest at a rate of 4.5%. How much will be in the account after 10 years? 3 of 14 Answer Original Ammount + Years x Original Ammount x Multiplying Factor For Interest Rate 450 + 10 x 450 x 0.045 = £9315 4 of 14 Questions Compound Interest This is when the interest earned is recalculated at the end of each year so the ammount added changes. £450 is deposited in a compound interest account which earns interest a rate of 4.5%. How much will be in the account after 10 years? 5 of 14 Answer 100 + 4.5 = 104.5% = 1.045 450 x 1.045 to the power of 10 = £4702.5 Original Ammount x (Multiplying Factor For The Increase 100 + Interest rate)Years To find the multiplying factor for a decrease do 100 - percentage then change to a decimal. 6 of 14 Question Finding A Total From A Percentage This involves using the fact that percentages are out of 100 to find the original 100%'s value. 15% of an ammount is £3.60. How much is the whole ammount? 7 of 14 Answer 5% = 3.60 divided by 3 = 1.20 100% = 3.60 divided by 3 x 20 = £24 8 of 14 Question Reversing Percentage In a sale a table cost £860. The sale says 20% off, how much would it have cost before the sale? 9 of 14 Answer 20% = 0.8 Original Ammount x 0.8 = Sale Price Original Ammount = 860 divided by 0.8 = £1075 80% = 860 100% = 860 divided by 0.8 = £1075 10 of 14 Question Writing As A Ratio Ensure the units are the same and then simplify as you would a fraction. Remember that the final answer should not contain decimals or units. Write 0.64kg to 320g as a ratio 11 of 14 Answer 640g : 320g 640 : 320 2 : 1 12 of 14 Question Using Ratios Using the fact that a ratio tells you how many parts belong to each item / person, link it to fractions to decide what to do. Share £35 in the ratio 2 : 5 13 of 14 Answer 2 + 5 = 7 parts 35 divided by 7 = £5 per 1 part 2 x 5 = £10 5 x 5 = £25 14 of 14
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