8 Proportion
Proportion is used to scale quantities up or down by the same ratio. This is shown in the following example – what happens if you want to adapt a favourite recipe to serve more people?
Example: Using proportion for more portions …
Here is a recipe for making a sponge cake for four people:
4 oz selfraising flour
4 oz caster sugar
4 oz butter
2 eggs
How much of each ingredient is needed to make a cake for eight people?
Method
To make a cake for eight people you need twice the amount of each ingredient:
8 oz selfraising flour (4 × 2)
8 oz caster sugar (4 × 2)
8 oz butter (4 × 2)
4 eggs (2 × 2)
Use the example above to help you with the following activity. Remember to check your answers once you have completed the questions.
Activity 38: Scaling up recipes
 This recipe makes ten large cookies:
 220 g selfraising flour
 150 g butter
 100 g caster sugar
 2 eggs
How much of each ingredient is needed to make 20 cookies?
 This recipe makes four servings of strawberry milkshake:
 800 ml milk
 200 g strawberries
 4 scoops of ice cream
How much of each ingredient is needed for two people?
 This recipe makes dessert for two people:
 300 ml milk
 60 g powder
How much of each ingredient is needed to serve six people?
Answer
 To make 20 cookies you need twice as much of each ingredient:
 440 g flour (220 × 2)
 300 g butter (150 × 2)
 200 g sugar (100 × 2)
 4 eggs (2 × 2)
 To make milkshakes for two people you need half as much of each ingredient:
 400 ml milk (800 ÷ 2)
 100 g strawberries (200 ÷ 2)
 2 scoops of ice cream (4 ÷ 2)
 To make dessert for six people you need three times the amount of each ingredient:
 900 ml milk (300 × 3)
 180 g powder (60 × 3)
Once you have checked your answers and have got them all correct, please have a go at the next activity.
Activity 39: Looking at ratio and proportion
Note: Calculators not allowed.

A label on a bottle of curtain whitener says that you should add one part concentrated curtain whitener to nine parts water.
How much curtain whitener and water is needed to make up a 2 000 ml solution?

Here is a recipe for a lowfat risotto for two people:
 200 g mushrooms
 175 g rice
 180 ml water
 180 ml evaporated milk
 Salt and pepper
How much of each ingredient is needed if you want to cook enough risotto for six people?
Answer

A ratio of 1:9 means one part curtain whitener to nine parts water, making ten parts in total.
You need 2 000 ml of solution. If ten parts are worth 2 000 ml, this means that one part is worth:
 2 000 ml ÷ 10 = 200 ml
So 2 000 ml of solution requires:

Curtain whitener: one part × 200 ml = 200 ml
Water: nine parts × 200 ml = 1 800 ml
You can confirm that these figures are correct by adding them and checking that they match the amount needed:
 200 ml + 1 800 ml = 2 000 ml
 To make enough risotto for six people you need three times as much of each ingredient:
 600 g of mushrooms (200 × 3)
 525 g of mushrooms (175 × 3)
 540 ml of water (180 × 3)
 540 ml of evaporated milk (180 × 3)
Summary
In this section you have learned how to use proportion to solve simple problems in everyday life, for example when adapting recipes.