1. Learning about Using Inverse Operations for finding the original price after a percentage increase or decrease

2. To find a percentage of a number, you.. Divide the percent by 100 And multiply by the number 12% of 40 = 12  100 (= 0.12) X 40 = 4.8 Notice that  100 changes the % to a decimal

3. If you wanted to increase 40 by 12% Find 12% of 40 and then add this answer to 40 112% of 40 = 4.8 + 40 112  100 (= 1.12) X 40 = 44.8 Notice that 112  100 changes the % to a decimal which is 1.12 The increased amount is (100 + 12)% of the original

4. If you wanted to decrease £125 by 23% Find 23% of 125 and then subtract this answer from 125 77  100 (= 0.77) X 125 = £96.25 Notice that 77  100 changes the % to a decimal which is 0.77 The reduced amount is (100 - 23)% of the original 23  100 x 125 = 28.75 £125 - £28.75 = £96.25

5. InputOutput 40 X 0.12 4.8 4044.8 X 1.12 To increase by a percentage

6. Input Output ? X 1.12 44.8 Insurance costs have increased by 12%The cost after the increase is £44.80 What was the cost before the increase?  1.12 44.8 40 It cost £40 before the increase Using inverse operations!

7. Input Output ? X 1.23 88.56 Insurance costs have increased by 23%The cost after the increase is £88.56  1.23 88.56 72 It cost £72 before the increase Using inverse operations! What was the cost before the increase?

8. Input Output 125 X 0.23 28.75 125 X 0.77 96.25 To decrease by a percentage What is £125 minus £28.75?

9. InputOutput ? X 0.77 96.25 In a sale stock is reduced by 23%The sale price of a suit is £96.25  0.77 96.25 125 It cost £125 before the sale The sale price is (100-23)% of the original price Using inverse operations! What was the cost before the increase?

10. Input Output ? X 0.82 96.25  0.82 96.25 117. 38 It cost £117.38 before the sale The sale price is (100-18)% of the original price Round to 2dp for money! What was the cost before the increase? In a sale stock is reduced by 18%The sale price of a suit is £96.25 Using inverse operations!