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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
Share activities with pupils

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.

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.

Keywords

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

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).

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 %