Scaling a recipe
Ratios and proportion. Play first, formula later.
Pancakes for the whole family
The recipe says it feeds 4 people. But today you might be cooking for one, or for a street party. How much of everything do you need?
How many people are you feeding?
What you need
Each coloured block is one person's share. Every block is exactly the same size.
Flour : Milk is always
2 : 3
no matter how many people
Drag the slider again, then pick what stays the same
The shortcut you've just been using
Because each person's share never changes, you can find any amount by multiplying:
new amount = original amount × (new people ÷ original people)
Example: 200 g of flour for 4 people. For 10 people that's 200 × (10 ÷ 4) = 500 g. This idea is called proportion, and the "per person" amount is the unit rate.
Try it with a different problem
Working backwards uses the same idea: divide by the per-person amount (50 g).
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