New
New
Year 7
Determining the whole
I can determine the whole, given one part and the ratio
New
New
Year 7
Determining the whole
I can determine the whole, given one part and the ratio
Lesson details
Key learning points
- A bar model can help to represent the situation.
- A ratio table can also be used to help show the multiplicative relationship.
- Both representations help to expose the structure.
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.
During the 2nd learning cycle pose a question e.g. 'The ratio of red:blue cars in a car park is 2:5. Sofia counts the number of blue cars in car park. She counts 9 blue cars. How do you know she has miscounted? How many do you think there were?'''
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.
Fill in the missing word: are in proportion if they have a constant multiplicative relationship.
Q2.
Share 189 in the ratio 2 : 7. Which is a correct first step in solving this problem?
189 ÷ 5
189 ÷ 7
189 ÷ 8
Q3.
Izzy and Andeep share 189 stickers in the ratio of 2 : 7. How many stickers does Izzy get?
Q4.
Share 132 in the ratio 4 : 6 : 1. What is the value of the largest share?
Q5.
The ratio of flour to butter to sugar in a cookie recipe is 3 : 2 : 1. You want to make a giant cookie weighing 540 grams. How much flour will you need?
Q6.
The perimeter of a triangle is 32.4 cm. The sides are in the ratio 3 : 8 : 7. How long is the longest side?
Exit quiz
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6 Questions
Q1.
Write the ratio 3 to 5 using the correct notation.
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. Sam gets 45 stickers, how many stickers are there in total?
Q4.
Laura, Jacob and Jun share some sweets in the ratio 5 : 8 : 3. Jun gets 9 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 16 red 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 longest side is 9.6 cm, what is the perimeter of the triangle?