Question 1130447
Solve and verify your answer. 
A sludge pool is filled by two inlet pipes.
 One pipe can fill the pool in 10 days and 
 the other pipe can fill it in 25 days.
 However, if no sewage is added, waste removal will empty the pool in 36 days.
 How long (how many days), will it take the two inlet pipes to fill an empty pool?
:
Let t = time in days to fill the pool
let the competed job (a full pool) = 1
:
Each will do a fraction of the job, the 3 fractions will add up to 1
waste removal will be negative.
{{{t/10}}} + {{{t/25}}} - {{{1/36}}} = 1
multiply equation by LCM, 1800, to get rid of the denominators
180t + 72t - 50t = 1800
202t = 1800
t = 1800/202
t = 8.91 days