A small pump can drain a pool in 9 hours. A large pump could drain the same pool in 3 hours. How long (to the nearest minute) will it take to drain the pool if both pumps are used simultaneously?

22.5 hours

Step-by-step explanation:

Let t be the time taken by both of the pumps to drain the pool.

Given: Time taken by pump 1 to drain the pool alone= 9 hours.

Time taken by pump 2 to drain the pool alone= 3 hours.

If  both pumps are used simultaneously, then

Hence, it will take 22.5 hours to drain the pool if both pumps are used simultaneously.