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Year 8

Increase by a percentage

I can calculate percentage changes (increase).

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New
New
Year 8

Increase by a percentage

I can calculate percentage changes (increase).

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. A bar model can be used to find a percentage increase.
  2. A double number line can be used to find a percentage increase.
  3. A ratio table can be used to find a percentage increase.

Common misconception

A single digit percentage is incorrectly worked out by dividing by 10 and not 100 e.g 3% = 0.3. This error continues when increasing amounts e.g increase 40 by 3% has a multiplier of 1.3

Remind pupils that to covert a percentage into a decimal we divide by 100. This applies with increase too e.g 120% has a multiplier of 1.2

Keywords

  • Proportionality - If two things are proportional then the ratio of part to whole is maintained and the multiplicative relationship between parts is also maintained.

Using mini-whiteboards, for example, students must draw the same question but illustrated in different ways; ratio table, double number line or bar model. E.g Increase 800 by 55%. They can then decide which representation they prefer. Look out for efficient approaches e.g 50% + 5%
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.
Match each percentage statement to its value.
Correct Answer:20% of 240,48

48

Correct Answer:10% of 240,24

24

Correct Answer:20% of 300,60

60

Correct Answer:40% of 240,96

96

Correct Answer:30% of 240,72

72

Correct Answer:10% of 300,30

30

Q2.
22% of 84 is .
Correct Answer: 18.48
Q3.
31% of 750 is .
Correct Answer: 232.5, 232.50
Q4.
Which of the following calculations is equivalent to 12% of 300?
Correct answer: 0.12 × 300
12 × 300
Correct answer: 30 + 6
12 × 100
30 + 3
Q5.
Match each calculation with the correct percentage statement.
Correct Answer:0.32 × 560,32% of 560

32% of 560

Correct Answer:0.41 × 560,41% of 560

41% of 560

Correct Answer:0.032 × 560,3.2% of 560

3.2% of 560

Correct Answer:0.041 × 560,4.1% of 560

4.1% of 560

Q6.
19% of 84 is .
Correct Answer: 15.96

Exit quiz

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6 Questions

Q1.
Increase 400 by 20%.
Correct Answer: 480
Q2.
Increase 70 by 30%.
Correct Answer: 91
Q3.
Match each percentage increase question with an equivalent question.
Correct Answer:Increase 450 by 2%,Work out 102% of 450

Work out 102% of 450

Correct Answer:Increase 450 by 20%,Work out 120% of 450

Work out 120% of 450

Correct Answer:Increase 450 by 12%,Work out 112% of 450

Work out 112% of 450

Correct Answer:Increase 450 by 1.2%,Work out 101.2% of 450

Work out 101.2% of 450

Q4.
Match each statement with the correct multiplier.
Correct Answer:Increase by 88%,×1.88

×1.88

Correct Answer:Increase by 8.8%,×1.088

×1.088

Correct Answer:Increase by 80%,×1.8

×1.8

Correct Answer:Increase by 8%,×1.08

×1.08

Q5.
139% of 600 is .
Correct Answer: 834
Q6.
Increase 800 by 11% and then by 10%.
Correct Answer: 976.8, 976.80