Question

There are 21 animals in the barn. Some are ducks and some are horses. There are 72 legs in all. How many of each animal

are there?

Answer 1

• 15 horses
• 6 ducks

Explanation:

Let x represent the number of horses. Then the number of ducks is
`21-x` and the number of legs is ...

`4x +2(21 -x) = 72`

`2x +42 = 72` . . . . . . . simplify

`x +21 = 36` . . . . . . divide by 2

`x = 15` . . . . . . . . . subtract 22; the number of oxen

`22-x = 6` . . . . . the number of ducks

There are 6 ducks and 15 horses in the barn.