Question

Two pipes can fill a tank in 10 hours and 12 hours respectively while a third pipe empties the full tank in 20 hours. If all the three pipes operate simultaneously, in how much time the tank will be filled?

• A. 7 hrs
• B. 8 hrs
• C. 7 hrs 30 min
• D. 8 hrs 30 min.

Answer 1

The correct option is C 7 hrs 30 min

Net part filled in 1 hour

$=(\frac{1}{10}+\frac{1}{12}-\frac{1}{20})=\frac{8}{60}=\frac{2}{15}$

$\therefore$ The tank will be full in 15/2 hrs.
= 7 hrs 30 min.