Math & Logic · Ages 7–9
Riddle #71
A farmer's field has only ducks and cows in it. The farmer counts 5 heads and 14 legs. How many ducks and how many cows are in the field?
You solved this one before
Answer: 3 ducks and 2 cows
Five heads means five animals. Draw five animals and give each one 2 legs — that is only 10, so 4 legs are still spare. Each cow needs 2 legs more than a duck, so the spare 4 legs make 2 cows, and the other 3 are ducks. Check it: (3 × 2) + (2 × 4) = 14.