New
New
Year 10
Higher
Checking and securing understanding of percentage decrease
I can decrease an amount by a given percentage.
New
New
Year 10
Higher
Checking and securing understanding of percentage decrease
I can decrease an amount by a given percentage.
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Lesson details
Key learning points
- In all of these representations a single multiplier can be used to find a percentage decrease.
- Representation can help when you are not using a calculator.
- A multiplier is significantly faster when using a calculator.
- To decrease you are going below the original amount.
Keywords
Proportion - If two things are proportional then the ratio of part to whole is maintained and the multiplicative relationship between parts is also maintained.
Common misconception
When using multipliers, pupils can mistake a decimal for the percentage decrease. e.g. 0.52 is a 52% decrease, rather than recognising a 48% decrease
Reminding students that a decimal multiplier greater than 1 means an increase, and a decimal multiplier less than 1 means a decrease. The latter requires a subtraction from 1 or 100%
To embed the fact that many questions can be the same but written indifferent ways, get pupils to write as many different questions to a calculation on MWB e.g 0.65 x 500 = 65% of 500 = 500 decreased by 500. Conversely, when an answer is 0.52, this says it is a decrease of 48% of 52% of an amount.
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.
Increase 600 by 5%
Q2.
Write 62 as a percentage of 200
Q3.
Increase 90 by 11%
Q4.
Find 11% of 700
Q5.
Write 50 as a percentage of 1250
Q6.
Find 90% of 625
Exit quiz
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6 Questions
Q1.
Which statement is the equivalent of "Decrease 50 by 20%"?
Work out 20% of 50
Divide 50 by 20
Q2.
Which statement is the equivalent of "Increase 130 by 15%"?
Work out 85% of 130
Work out 15% of 130
Q3.
Which statement is the equivalent of "Decrease 700 by 35%"?
Work out 35% of 700
Work out 85% of 700
Q4.
Decrease 700 by 4.5%
Q5.
Increase 700 by 4.5%
Q6.
Increase 700 by 18%