Percentages Objectives: B GradeUnderstand how to calculate successive percentages Work out compound interest Prior knowledge: Understand : Finding percentages of quantities – calculator and non calculator Percentage increase / decrease & percentage multipliers

Percentages Successive increase or decrease questions will have a percentage increase / decrease that is repeated more than once. Example: £1000 is put in a bank account that pays 5% interest at the end of each year. Calculate how much there will be after 3 years. At the end of the first year there will have been a 5% increase Answer: The percentage multiplier for a 5% increase is: 1.05 Original quantity × percentage multiplier = new quantity 1000 × 1.05 =1050 At the end of the second year there will have been a 5% increase 1050 × 1.05 = At the end of the third year there will have been a 5% increase × 1.05 = £

Percentages Look at what has been done here 1000 × 1.05 This can be simplified to The index number represents the number of times the percentage change is repeated 1000 × % of 1000 Look at the difference by calculating one year’s percentage increase Then multiplying it by × 0.05 = 50 = £ = ( ) × × 3 = This is called simple interest because it does not calculate 5% of the new quantity at the end of the first year