Determining the part
Lesson details
Learning outcome
I can determine one part, given the other part and the ratio.
Key learning points
- It is not necessary to calculate the total original amount.
- Different representations have different limitations.
- A bar model can be very effective here.
Keywords
Proportion - Variables are in proportion if they have a constant multiplicative relationship.
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.
Common misconception
Always dividing the amount by the sum of the 'parts' of the ratio to get one 'part'.
Offer opportunities to match problems to bar models, ensure the same numbers are used to highlight the differences.
Teacher tip
Challenge pupils to come up with context questions which do not work. This should help to encourage them to consider the reasonableness of their answers.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.How is 6 : 11 read aloud in words?
Q2.What number is represented by the question mark in this bar model?
Q3.Sam and Aisha share some stickers in the ratio of 3 : 5. Aisha gets 25 stickers, how many stickers are there in total?
Q4.Laura, Jacob and Jun share some sweets in the ratio 5 : 6 : 3. Jacob gets 24 sweets, how many sweets are there in total?
Q5.Lucas is making necklaces with red, blue and white beads in the ratio 2 : 7 : 5. He uses 15 white beads. How many beads are on each necklace?
Q6.The lengths of the sides of a triangle are split in the ratio 3 : 8 : 7. The shortest side is 6.6 cm, what is the perimeter of the triangle?
Assessment exit quiz
6 Questions
Q1.Complete the sentence: When using a bar model the parts must be .
Q2.What number is represented by the question mark in this bar model?
Q3.A bunch of flowers contains red and yellow flowers in the ratio 3 : 5. There are 9 red flowers. How many yellow flowers are in the bunch?
Q4.The ratio of flour to butter to sugar in a cookie recipe is 3 : 2 : 1 . You use 180g of flour. How much butter is used?
Q5.Andeep, Sam and Sofia share some sweets in the ratio 3 : 8 : 5 Sofia gets 20 sweets, how many does Andeep get?
Q6.The lengths of the sides of a triangle are split in the ratio 3 : 8 : 7 The longest side is 4.8 cm, what is the length of the shortest side?
To help you plan your 7 maths lesson on: Determining the part, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 7 maths lesson on: Determining the part, 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: fractions and ratio unit, dive into the full secondary maths curriculum, or learn more about lesson planning.