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Year 7

Securing understanding of ratio as a multiplicative relationship

I can reason about ratios in a context.

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New

Year 7

Securing understanding of ratio as a multiplicative relationship

I can reason about ratios in a context.

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Share activities with pupils

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Lesson details

Key learning points

A ratio describes as connection between two values.
This relationship is multiplicative, not additive.
Adding the same amount to each part of the ratio changes the ratio.

Keywords

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

Using multiplication as repeated addition leads to incorrect additive strategies of ratios.

Focus on the multiplicative relationships between parts to whole or whole to parts. Ratio allow the multiplicative relationship to be seen.

Discuss the different types of chocolate. What is dark chocolate? What different types of dark chocolate is there? Why do they taste different? This is due to the percentage of cocoa. Also discuss milk chocolate.

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).

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Starter quiz

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6 Questions

Q1.

Use the ratio table to work out how many slices of cheese are needed to make 7 sandwiches. slices.

Correct Answer: 21, twenty one, 21 slice, 21 slices

Q2.

Use the ratio table to work out how many slices of cheese are needed when there are 12 slices of tomato. slices.

Correct Answer: 24, twenty four, twentyfour

Q3.

Here is a recipe for vanilla cake. How much sugar is needed if you use 6 eggs? grams of sugar.

Correct Answer: 225, 225, 225 g, 225 grams

Q4.

Here is a recipe for vanilla cake. How much vanilla is needed if you use 125 g of flour? ml of vanilla.

Correct Answer: 5, 5ml, 5 ml, 5 millilitres

Q5.

Lucas has some red and blue marbles. For every 4 red marbles, he has 5 blue marbles. Lucas has 20 red marbles altogether. Lucas has blue marbles.

Correct Answer: 25, twenty five

Q6.

Laura has some red and blue marbles. For every 4 red marbles, she has 5 blue marbles. She has 36 marbles altogether. Laura has blue marbles.

Correct Answer: 20, twenty

Exit quiz

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6 Questions

Q1.

A ratio shows the relative sizes of 2 or more values and allows you to compare a part with another part in a whole. The relationship between parts and/or the whole is always .

additive

Correct answer: multiplicative

constant

subtractive

Q2.

A robot in travelling around a toxic planet. The protective clothing is heavy, so for every 6 protective items, there must be 2 batteries. Match the equipment list to its effect on the robot.

Correct Answer:18 protective and 6 batteries,This means the robot is fully protected and quick.

This means the robot is fully protected and quick.

Correct Answer:3 protected and 2 batteries,This means the robot is quick but not fully protected.

This means the robot is quick but not fully protected.

Correct Answer:12 protected and 2 batteries,This means the robot protected but slow.

This means the robot protected but slow.

Q3.

To make a "Sunrise" orange paint, 2 cans of yellow paint for every 1 can of red paint is used. Match the paint shades to the recipes.

Correct Answer:"Sunrise" Orange,4 cans of yellow and 2 cans of red

4 cans of yellow and 2 cans of red

Correct Answer:Darker than "Sunrise" orange,6 cans of yellow and 4 cans of red

6 cans of yellow and 4 cans of red

Correct Answer:Lighter than "Sunrise" orange,10 cans of yellow and 4 cans of red

10 cans of yellow and 4 cans of red

Q4.

To make lemonade, 1 lemon and 2 tablespoons of sugar are used for every 500 ml of water. Jun uses 750 ml of water to make lemonade. Jun should use tablespoons of sugar.

Correct Answer: 3, three

Q5.

Select all the statements that are correct.

Correct answer: A ratio describes the relationship between values.

Ratio uses an additive relationship.

Adding the same amount to each part in a ratio keeps the ratio the same.

Correct answer: Multiplying the same amount to each part in a ratio keeps the ratio the same.

Q6.

"Choko Milk chocolate" bars are made with 2 parts cocoa, 5 parts milk powder and 1 part sugar. Too much cocoa makes it too bitter, too much sugar makes it too sweet. Match each result with its recipe

Correct Answer:Too sweet,18 parts cocoa, 45 parts milk powder and 10 parts sugar.

18 parts cocoa, 45 parts milk powder and 10 parts sugar.

Correct Answer:Too bitter,15 parts cocoa, 35 parts milk powder and 7 parts sugar.

15 parts cocoa, 35 parts milk powder and 7 parts sugar.

Correct Answer:Perfect,10 parts cocoa, 25 parts milk powder and 5 parts sugar.

10 parts cocoa, 25 parts milk powder and 5 parts sugar.

Correct Answer:Too much milk powder,20 parts cocoa, 55 parts milk powder and 10 parts sugar.

20 parts cocoa, 55 parts milk powder and 10 parts sugar.