Learn the 3-Step Method
1Find the factor (or go via 1).
4 → 6 people is × 1.5. Or one person's amount: 200 ÷ 4 = 50 g.
2Scale EVERY ingredient.
Flour 300 g, and the same × 1.5 for eggs, milk, butter — no favourites.
3Halve-and-add shortcut.
1.5 × anything = the amount + half of it: 200 + 100 = 300.
Worked Example
A recipe for 4 uses 2 eggs and 300 ml milk. Scale it for 10 people.
Watch Out! Common Mistakes
Scale, don’t add! One and a half times the people needs one and a half times the flour: 300 g.
Everything! Extra flour with the old amount of milk ruins pancakes AND ratio questions. One factor for every line.
Real-world note: 2.5 eggs for 5 people? In exams keep the exact value; in kitchens round sensibly and say so.
⬇ Cheat Sheet
- Factor = new people ÷ old people.
- Multiply EVERY ingredient by it.
- Or go via one person's amounts.
- ×1.5 shortcut: add half again.
📖 Continue Your Journey
Quick summary
- Scale factor = new servings ÷ original servings.
- Multiply every ingredient by the same factor.
- Or go through one person's portion and multiply up.
- ×1.5 means 'add half again': 200 g → 300 g.
Frequently asked questions
How do you scale a recipe up?
Divide the new number of servings by the original to get the factor (4 → 6 is ×1.5), then multiply every ingredient by it.
What if the factor is awkward?
Go through one serving: divide each ingredient by the original servings, then multiply by the new number — the unitary method again.
Why do recipe questions appear in the 11+?
They test proportional reasoning in a real context, often with a trap answer from adding instead of scaling.
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