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Published byGeorge Dickerson Modified over 7 years ago

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**Objective To calculate percentage increase and decrease.**

Percentages Objective To calculate percentage increase and decrease.

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**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

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**Method 1 Example: Increase £8 by 5% Find 5% of £8: 5 x 800p = 40p 100**

Then add 40p to the original amount £8.40

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**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% 1st then 1% etc…

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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%

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**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

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**Method 1 Example: Decrease £8 by 7% Find 7% of £8: 7 x 800p = 56p 100**

Then take 56p off the original amount £7.44 (Without a calculator)

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**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% 1st then 1% etc…

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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 81.9p 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

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**Question Practice Exam style Questions Chapter 5 – Page 142**

Exercise 5E Q 8 Exercise 5F Q 10

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**Overview What have we learnt today?**

Are we confident in answering questions on this part of the topic?

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**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

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**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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