Percentages Objective To calculate percentage increase and decrease.
Percentage Increase Two methods how to increase a percentage Method 1 – Find the increase and add it to the original amount Method 2 – Using a multiplier
Method 1 Example: Increase £ 8 by 5% Find 5% of £ 8: 5 x 800 p = 40 p 100 Then add 40 p to the original amount £ 8. 40
Method 2 Example: Increase £ 8. 50 by 7% A 7% increase is a multiplier of 1. 07 Therefore £ 8. 50 x 1. 07 = £ 9. 10 Straightforward – use calculator method, or find 10% 1 st then 1% etc…
Examples to complete • Bonus paid on salary of 3%, salary £ 1, 200, what is the total salary? • An item costs £ 6. 50 without VAT at 17. 5%, what is the total cost? • Increase £ 50 by 60% • House Price Increase – 12%, 15%
Percentage Decrease Two methods how to decrease a percentage Method 1 – Find the decrease and take it away from the original amount Method 2 – Using a multiplier
Method 1 Example: Decrease £ 8 by 7% Find 7% of £ 8: 7 x 800 p = 56 p 100 Then take 56 p off the original amount £ 7. 44 (Without a calculator)
Method 2 Example: Decrease £ 8. 50 by 7% A 7% decrease is a multiplier of 0. 93 Therefore £ 8. 50 x 0. 93 = £ 7. 90 Straightforward – use calculator method, or find 10% 1 st then 1% etc…
Examples to complete • Car valued at £ 13, 500 when new, it lost 22% depreciation in the first year. What is it’s value? • Petrol Costs 81. 9 p per litre. What does it cost after a 2. 4% decrease? • A scooter costs £ 24, but is reduced in a sale by 20%, what is the sale price? • House Decrease
Question Practice Exam style Questions Chapter 5 – Page 142 Exercise 5 E Q 8 Exercise 5 F Q 10
Overview What have we learnt today? Are we confident in answering questions on this part of the topic?
What if the question doesn’t give the % Decrease? Example - I achieved 66% in the first test and 64% in the second, what is the percentage increase? Percentage Decrease = actual decrease x 100% initial value % decrease = 2 x 100% = 3% 66
What if the question doesn’t give the % Increase? Example - I achieved 54% in the first test and 72% in the second, what is the percentage increase? Percentage Increase = actual increase x 100% initial value % increase = 18 x 100% = 33% 54
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