Question 799694
Two inlet pipes can fill an empty swimming pool in 3 days and 6 days, respectively.
 A pump can empty a full pool in 4 days.
 How long will it take to fill the empty pool if both pipes are open and the pump is on?
:
let t = time required to fill the pool in this situation
let the full pool = 1
:
{{{t/3}}} + {{{t/6}}} - {{{t/4}}} = 1
Multiply by 12 to get rid of the denominators, results:
4t + 2t - 3t = 12
3t = 12
t = 12/3
t = 4 days to fill the pool