Scaling means making something bigger or smaller by the same amount for every part. If you make twice as much, you double every ingredient. If you make half as much, you halve every ingredient.
Why this matters: Cooking for a big family, mixing squash and water, or working out how many grown-ups you need on a school trip all use scaling and simple ratio.
Scaling a recipe
A pancake recipe for 2 people uses 4 spoons of flour. To make it for 4 people (twice as many), you double it: 4 × 2 = 8 spoons.
| People | Flour |
|---|---|
| 2 | 4 spoons |
| 4 | 8 spoons |
| 1 | 2 spoons |
"For every" language
We can say for every 1 cup of rice, use 2 cups of water. So for 3 cups of rice you need 6 cups of water, because you multiply both parts by 3.
For every 1 adult there are 6 children.
If there are 2 adults, there are 2 × 6 = 12 children.
If there are 18 children, that needs 18 ÷ 6 = 3 adults.
If there are 2 adults, there are 2 × 6 = 12 children.
If there are 18 children, that needs 18 ÷ 6 = 3 adults.
Simple ratio
A ratio like 1 : 6 means "1 to 6". On a trip with 1 adult to 6 children, a group of 24 children needs 24 ÷ 6 = 4 adults.