Decrease by a percentage
Lesson details
Learning outcome
I can calculate percentage changes (decrease).
Key learning points
- A bar model can be used to find a percentage decrease.
- A double number line can be used to find a percentage decrease.
- A ratio table can be used to find a percentage decrease.
- In all of these representations a single multiplier can be used to find a percentage decrease.
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.
Common misconception
Pupil can often get confused with increasing and decreasing an amount e.g Increase 45 by 23% and decreasing 45 by 23% have the same multiplier.
Encourage students to draw double number lines or ratio tables so they can see the increase and multiplier or decrease and multiplier.
Teacher tip
To embed the understanding 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 = 50% of 650 e.g 1.23 x 400 = increase 400 by 23% = find 123% of 400.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.40% of 120 is .
Q2.22% of 520 is .
Q3.31% of 440 is .
Q4.Which of the following calculations is equivalent to 49% of 200?
Q5.Match each calculation with the equivalent percentage statement.
12% of 560
21% of 560
1.2% of 560
2.1% of 560
Q6.19% of 840 is .
Assessment exit quiz
6 Questions
Q1.Decrease 40 by 20%.
Q2.Decrease 700 by 30%.
Q3.Match each question to an equivalent question.
Work out 88% of 450
Work out 80% of 450
Work out 20% of 450
Work out 98.8% of 450
Q4.Match each statement with the correct multiplier.
×0.78
×0.98
×0.2
×0.92
Q5.Decrease 600 by 39%.
Q6.Match each calculation to its answer.
363.4
384
68.6
352
To help you plan your 8 maths lesson on: Decrease by a percentage, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 8 maths lesson on: Decrease by a percentage, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 3 maths lessons from the Understanding multiplicative relationships: percentages and proportionality unit, dive into the full secondary maths curriculum, or learn more about lesson planning.