Through the first pipe, you can pump out the pool in 10 hours, through the second in 12 hours

Through the first pipe, you can pump out the pool in 10 hours, through the second in 12 hours, and through the third in 15. How much can you pump out the pool with three pipes?

Data: t1 (duration of operation of the first pipe) = 10 hours; t2 (duration of operation of the second pipe) = 12 hours; t3 (duration of the third pipe) = 15 hours; A (amount of work performed) = 1 (1 pool pumped out).

1) Pump performance (Px = A / tx): P1 = 1/10; P2 = 1/12; P3 = 1/15.

2) Overall performance: P = P1 + P2 + P3 = 1/10 + 1/12 + 1/15 = 0.25.

3) Duration of pumping out the pool with three pipes: t = A / P = 1 / 0.25 = 4 hours.

Answer: The pool can be pumped out with three pipes in 4 hours.