Subject: General Aptitude · Chapter: Pipes and Cisterns · Exam: · Marks: · Difficulty:
Two taps A and B can fill a tank in 5 hours and 20 hours respectively. If both the taps are open then due to a leakage, it took 30 minutes more to fill thetank. If the tank is full, how long will it take for the leakage alone to empty the tank?
(a)$4 \frac{1}{2} \mathrm{hrs}$
(b)9 hrs
(c)18 hrs
(d)36 hrs
Answer
Answer (as printed): D
Explanation
Part filled by (A+B) in 1 hour $= \left(\frac{1}{5}+\frac{1}{20}\right) = \frac{1}{4}$. So, A and B together can fill the tank in 4 hours. Work done by the leak in 1 hour $= \left(\frac{1}{4}-\frac{2}{9}\right) = \frac{1}{36}$. $\therefore$ Leak will empty the tank in 36 hours.
Explanation as extracted from the printed page; notation may be imperfect.