What it shows
A recipe is a set of ratios, so halving or doubling it means multiplying every amount by the same number. You rewrite a simple recipe for 2, 4 and 10 people and practise fractions and unit conversion.
The science
A ratio compares two amounts, and equivalent ratios are found by multiplying both by the same number. To serve twice as many people, every ingredient is doubled; to serve half as many, each is halved. Fractions like three quarters of a cup are parts of a whole cup that you must add or multiply correctly.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A simple recipe, such as poha or lemonade, for 4 people
- Measuring cups and spoons
- A notebook
- A kitchen scale
- A pencil
- A calculator
- An adult to supervise any cooking
Safety
For this project: An adult must handle the stove and knives. Children measure, calculate and write only. Check for food allergies in your family.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Copy the recipe and the amount of each ingredient for 4 people.
Decide how many people you want to serve, and find the multiplier by dividing it by four.
Multiply each ingredient by the multiplier and write the new amount.
Convert amounts to a convenient unit, such as 1,000 ml for a litre, when the numbers get large.
Check your answer by measuring one of the scaled amounts with the cups.
Draw a scale table for 2, 4, 8 and 12 people.
Cook the half-size recipe with an adult and compare the taste to the original.
What you should see
Your table shows each ingredient for different numbers of people, and the half-size dish tastes the same as the full dish. The multiplier method works for any recipe.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is a ratio?
A comparison of two quantities.
2How much is 3/4 cup doubled?
1 and a half cups.
3How do you scale a recipe for 6 people from 4?
Multiply each amount by one and a half.
4Why measure carefully?
The taste depends on the ratio of ingredients.
Take it further
Find the cost of the recipe per person using the prices of ingredients.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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