1. Percentages Objectives: B GradeWork out reverse percentage problems Prior knowledge: Understand : Finding percentages of quantities – calculator and non calculator Percentage increase / decrease & percentage multipliers Rearranging equations

2. Percentages The method of working out percentage increase / decrease is Original quantity × percentage multiplier = new quantity Reverse percentage problems will give the new quantity and you need to work out the original quantity To calculate the original quantity we rearrange the equation Original quantity percentage multiplier = new quantity ×

3. Percentages Example 1: Irene paid £38.70 for a skirt that had been reduced by 10% a sale. What was the original price? Original quantity × 0.9 = 38.70 Original quantity = 38.70 0.9 Original quantity = £43

4. Percentages Example 2: Jack received a 3.5% pay rise. His new salary is £12 420 Original quantity × 1.035 = 12 420 Original quantity = 12420 1.035 Original quantity = £12 000

5. Percentages Now do these: 1.A quantity is decreased by 3%. It is now 38.8. What was the original value? 2. A coat was advertised in a sale at £79 after a 5% reduction. What was the original price? 3. Nobby’s salary was increased by 7%. His new salary after the pay rise is £28 890. What was his original salary? 4. In a local election Labour received 1375 votes. This was 12% up on the previous election. What was their previous number of votes. 5. A charity’s income has been reduced by 12.5%. It’s income is now £49 000 per year. What was it’s previous revenue £56 000 12281375 1.12 49000 0.875 £27 000 28890 1.07 £83.16 79 0.95 40 38.8 0.97