Combining ratios
I can combine ratios.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- There may be a relationship between quantities A and B and a relationship between quantities B and C
- Therefore there is a relationship between A and C
- If A : B and B : C then A : B : C and A : C
- When the common quantity is not the same in each ratio, equivalent ratios can be used
- For example, if A:B and 2B:5C then 2A:2B:5C and 2A:5C
Keywords
Proportion - A part to whole (sometimes part to part) comparison. If two things are proportional then the ratio of part to whole is maintained and the multiplicative relationship between parts is also maintained.
Ratio - A ratio shows the relative sizes of 2 or more values and allows you to compare a part with another part in a whole.
LCM - LCM is an abbreviation for lowest common multiple.
Lowest common multiple - The lowest common multiple is the lowest number that is a multiple of two or more numbers.
Common misconception
Combining ratios without using equivalent ratios to equate the common part.
Pupils may need to spend extra time finding equivalent ratios and looking at when it is ok to combine ratios or not.
To help you plan your year 10 maths lesson on: Combining ratios, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 10 maths lesson on: Combining ratios, 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 4 maths lessons from the Ratio unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Lesson video
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Starter quiz
6 Questions
16 : 12
14 : 12
16 : 40
12 : 32
12 : 22
Exit quiz
6 Questions
