Question 886046
A tank is filled in 9 hours and drained in 11 hours. 
How long will it take to fill the tank if the drain is left half open?
:
If the drain is left half open, it should take 22 hrs to drain
:
let t = time to fill tank under the given conditions
let the completed job = 1 (a full tank)
fill is +, drain is -
{{{t/9}}} - {{{t/22}}} = 1
Multiply equation by 198, cancel the denominators and you have:
22t - 9t = 198
13t = 198
t = 198/13
t = 15.23 hrs