Percentages

1. Percentages Objectives: B Grade Work 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 = new quantity percentage multiplier Original 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. 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 Percentages 38.8 0.97 40 79 0.95 £83.16 28890 1.07 £27 000 1375 1.12 1228 49000 0.875 £56 000