New
New
Year 7
Determining the part
I can determine one part, given the other part and the ratio.
New
New
Year 7
Determining the part
I can determine one part, given the other part and the ratio.
Lesson details
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.
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.
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.
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.
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.
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?
Exit quiz
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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?