Working together ,two pumps can drain a certain pool in 3 hours.If it takes the older pump 12 hours to drain the pool by itself, how long will it take the newer pump to drain the pool on it’s own ?

Answer 1

3 hours(1/12 + x) = 1 job

3/12 + 3x = 1

3x = 9/12

x = (9/12)/(3/1) = (9/12)(1/3) = 9/36 = 1/4

The second pump can complete the job in 4 hours.

3(1/12 + 1/4) = 3(1/12 + 3/12) = 3(4/12) = 1