Two taps A and B can fill a tank in 5 hours and 20 hours respectively. If both the taps are open due to a leakage, it took 30 minutes more to fill the tank. If the tank is full, how long will it take for the leakage alone to empty the tank? Choose the correct answer
A) 5 hrs  B) 8 hrs  C) 9 hrs  D) 36 hrs  E) None
Sol.   Part filled by ( A + B ) in 1 hour = [1/5 + 1/20] = 1/4.   So, A and B together can fill the tank in 4 hours.   Work done by the leak in 1 hour = (1/4 - 2/9) = 1/36.   ∴ Leak will empty the tank in 36 hrs.   Answer 36 hrs
<result>D</result>
Two taps A and B can fill a tank in 5 hours and 20 hours respectively. If both the taps are open due to a leakage, it took 30 minutes more to fill the tank. If the tank is full, how long will it take for the leakage alone to empty the tank?