Question

When three pipes fill a pool, they can finish in 12 hours. Two of the pipes can finish in 18 hours if they are working together. How long would it take a third pipe to fill the pool on its own?

Answer 1

the number of pipes * the time is a constant proportional to the pool size.

3*12 = 2*18 = 1*36. So one pipe would take 36 hours.