Question

Working together two people can cut a lawn of grass in 5 hours. One person can do the job alone in 1 hour less than the other. How long would it take the faster person to do the job?

Answer 1

If the faster person takes x hours, then the slower person takes (x+1) hours. So, how much of the job gets done in an hour?

1/x + 1/(x+1) = 1/5

Now just find x.

Answer 2

21