Question

An inlet pipe on a swimming pool can be used to fill the pool in 15 hours

Answer 1

`18h`

1) According to the text, since we have a pipe to fill it in and a drain to empty the pool and we were told to find how long will it take to fill the pool we can write out the following rational equation:

`\begin{gathered} (t)/(15)-(t)/(40)=1-(1)/(4) \\ (t)/(15)-(t)/(40)=(3)/(4) \\ (120/15* t)/(120)-(120/40* t)/(120)=(30*3)/(120) \\ (8t)/(120)-(3t)/(120)=(90)/(120)*120 \\ 8t-3t=90 \\ 5t=90 \\ (5t)/(5)=(90)/(5) \\ t=18 \end{gathered}`

Note that since there is already 1/4 of the capacity of that pool, the sum of the filling pipe minus the draining pipe is going to be equal to 1 (full pool) - 1/4=3/4

2) So, the answer is:

`18h`