Question

A farmer owns pigs, chickens, and ducks. When all her animals are together, she has 30 feathered animals, and the animals all together have a total of 120 legs and 90 eyes. (All the animals have the expected number of parts.) How many of each animal might she have?

Answer 1

• 15 pigs
• 30 birds (might be 10 chickens and 20 ducks, or 15 of each)

Explanation:

The 30 feathered animals will have a total of 60 legs, so the remaining 60 legs belong to the pigs. There must be 15 pigs.

The numbers of eyes and legs give no information as to how the feathered animals are split between chickens and ducks. There are a total of 30 chickens and ducks, apparently including at least 2 of each (since the description is plural chickens and plural ducks).