Question

An inlet pipe on a swimming pool can be used to fill the pool in 38 hours. The drain pipe can be used to empty the pool in 40 hours. If the pool is 14 filled and then the inlet pipe and drain pipe are opened, how long from that time will it take to fill the pool?
Answer

Answer 1

To solve this problem you must apply the proccedure shown below:

1. In a hour you have $\frac{1}{38}$ of the pool filled and $\frac{1}{40}$.Taking $\frac{1}{4}$ of the pool filled, you have the following expression:

$\frac{1}{38}-\frac{1}{40}=\frac{1}{4}/t$

2. Solve for $t$, as following:

$t=\frac{760}{4}\\ t=190 hours$

The answer is: $190 hours$