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Securing understanding of ratio as a multiplicative relationship
I can reason about ratios in a context.
Lesson 2 of 17
New
New
- Year 7
Securing understanding of ratio as a multiplicative relationship
I can reason about ratios in a context.
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 (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Use the ratio table to work out how many slices of cheese are needed to make 7 sandwiches. slices.
Use the ratio table to work out how many slices of cheese are needed to make 7 sandwiches. slices.
Q2.Use the ratio table to work out how many slices of cheese are needed when there are 12 slices of tomato. slices.
Use the ratio table to work out how many slices of cheese are needed when there are 12 slices of tomato. slices.
Q3.Here is a recipe for vanilla cake. How much sugar is needed if you use 6 eggs? grams of sugar.
Here is a recipe for vanilla cake. How much sugar is needed if you use 6 eggs? grams of sugar.
Q4.Here is a recipe for vanilla cake. How much vanilla is needed if you use 125 g of flour? ml of vanilla.
Here is a recipe for vanilla cake. How much vanilla is needed if you use 125 g of flour? ml of vanilla.
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.
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.
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.
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.
Assessment exit quiz
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 .
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
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.
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.
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.
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.
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.
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.
Q5.Select all the statements that are correct.
Select all the statements that are correct.
Ratio uses an additive relationship.
Adding 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
"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
