New
New
Finding the percentage change
I can find the percentage increase or decrease given start and finish quantities.
Lesson 11 of 16
New
New
- Year 8
Finding the percentage change
I can find the percentage increase or decrease given start and finish quantities.
Lesson details
Key learning points
- The percentage change can be found using a bar model.
- The percentage change can be found using a double number line.
- 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 (2025), 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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Prior knowledge starter quiz
6 Questions
Q1.Which of the following words indicate an decrease?
Which of the following words indicate an decrease?
interest
profit
Q2.Which of the following is the correct calculation for finding 5% of 300?
Which of the following is the correct calculation for finding 5% of 300?
300 ÷ 0.5
300 × 0.5
300 ÷ 0.05
Q3.Match each question to the correct multiplier.
Match each question to the correct multiplier.
Q4.A t-shirt costs £13.50 in a sale offering a 25% discount. The cost of the t-shirt before the discount was £
A t-shirt costs £13.50 in a sale offering a 25% discount. The cost of the t-shirt before the discount was £
Q5.The value of a motorbike depreciates by 12% each year. It is now worth £6512. Last year the motorbike was worth £ .
The value of a motorbike depreciates by 12% each year. It is now worth £6512. Last year the motorbike was worth £ .
Q6.Mr. Oak sells a vase for £72. This gives him a 20% profit. Mr. Oak originally purchased the vase for £ .
Mr. Oak sells a vase for £72. This gives him a 20% profit. Mr. Oak originally purchased the vase for £ .
Assessment exit quiz
6 Questions
Q1.__________ is the decimal equivalent of a percentage.
__________ is the decimal equivalent of a percentage.
An addition
A division
A subtraction
Q2.100% = 36 and 120% = 43.2. The percentage change is %.
100% = 36 and 120% = 43.2. The percentage change is %.
Q3.The cost of a laptop decreases from £450 to £360. What is the percentage change?
The cost of a laptop decreases from £450 to £360. What is the percentage change?
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 %
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 %
Q5.Jacob’s score on a game increases from 3450 to 3726. The percentage change in Jacob's score is %.
Jacob’s score on a game increases from 3450 to 3726. The percentage change in Jacob's score is %.
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 %.
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 %.
