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Year 8

Finding the percentage change

I can find the percentage increase or decrease given start and finish quantities.

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New
New
Year 8

Finding the percentage change

I can find the percentage increase or decrease given start and finish quantities.

Download all resources
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Share activities with pupils
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Lesson details

Key learning points

  1. The percentage change can be found using a bar model.
  2. The percentage change can be found using a double number line.
  3. The percentage change can be found using a ratio table.

Keywords

  • Proportion - Variables are in proportion if they have a constant multiplicative relationship.

Common misconception

Forgetting to find the percentage change.

Emphasise the word change. Encourage pupils to write down the 2 percentages with their relevant values. Go back to the question and calculate the actual change they should notice that this is neither of the 2 values but the difference between them.

Use mini-whiteboards, for example, to highlight finding the change. Ask questions e.g. 'a bank account had a balance of £100, it now has a balance of £120. By how much has the amount changed?' and then move onto percentages. By what percentage has the value changed?'.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Which of the following words indicate an decrease?
Correct answer: depreciate
Correct answer: discount
interest
Correct answer: loss
profit
Q2.
Which of the following is the correct calculation for finding 5% of 300?
Correct answer: 300 × 0.05
300 ÷ 0.5
300 × 0.5
300 ÷ 0.05
Q3.
Match each question to the correct multiplier.
Correct Answer:Increase by 4%,×1.04

×1.04

Correct Answer:Decrease by 40%,×0.6

×0.6

Correct Answer:Decrease by 6%,×0.94

×0.94

Correct Answer:Increase by 60%,×1.6

×1.6

Q4.
A t-shirt costs £13.50 in a sale offering a 25% discount. The cost of the t-shirt before the discount was £
Correct Answer: 18, £ 18, 18.00, £18.00, £18
Q5.
The value of a motorbike depreciates by 12% each year. It is now worth £6512. Last year the motorbike was worth £ .
Correct Answer: 7400, 7 400, £7400, £7,400, 7,400
Q6.
Mr. Oak sells a vase for £72. This gives him a 20% profit. Mr. Oak originally purchased the vase for £ .
Correct Answer: 60, £60, 60.00, £60.00

Exit quiz

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6 Questions

Q1.
__________ is the decimal equivalent of a percentage.
An addition
A division
Correct answer: A multiplier
A subtraction
Q2.
100% = 36 and 120% = 43.2. The percentage change is %.
Correct Answer: 20, 20%, 20 %
Q3.
The cost of a laptop decreases from £450 to £360. What is the percentage change?
Correct answer: 20%
25%
80%
120%
125%
Q4.
Jun thinks of a number and decreases it by a percentage. The number Jun thought of was 160 and his new number is 136. Jun changed 160 by %
Correct Answer: 15, 15 %, 15%
Q5.
Jacob’s score on a game increases from 3450 to 3726. The percentage change in Jacob's score is %.
Correct Answer: 8%, 8 %, 8
Q6.
A reduced sugar bar of chocolate contains 35 g of sugar. The normal bar contains 15 g more of sugar. The sugar has been reduced by %.
Correct Answer: 30, 30%, 30 %