An easy question on chickens and rabbits for P2–P3, with a step-by-step solution, diagrams and the answer. One of the best-known Olympiad problem types: in the Hua Xia Cup it appears from the P2 first round to the P5 papers.
The question
In a cage on a farm there are 4 chickens and rabbits altogether.
Each chicken has 2 legs and each rabbit has 4.
There are 10 legs in all.
How many rabbits are there?
Show the hints (2)
💡Hint 1: Try it: if all 4 were chickens, how many legs would there be?
💡Hint 2: Swap one chicken for a rabbit. How many more legs is that?
Worked solution
Have a go first, then read the solution step by step.
1.If all were chickens: 4 × 2 = 8 legs, which is 10 − 8 = 2 too few.
2.Each swap adds 2, so there are 2 ÷ 2 = 1 rabbit.
⚠️Common mistake: working out 10 ÷ 4. The two kinds have different numbers of legs.
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