Question

Working alone, pump a can empty a pool in 3 hours. Working alone, pump b can empty the same pool in 2 hours. Working together, how many minutes will it take pump a and pump b to empty the pool?

Answer 1

Working alone pump A can empty the pool in 3 hours.

Working alone pump B can empty the same pool in 2 hours.

In one hour, pump A does 1/3 part of the work.

In one hour, pump B does 1/2 part of the work.

If they work together:

1/3 + 1/2 = 2/6 + 3/6 = 5/6

Taking the reciprocal, 6/5 is the time taken by pump A and pump B to empty the pool if they work together.

To convert hours to minutes:
6/5 × 60 = 72 minutes.

Pump A and pump B takes 72 minutes to empty the pool.