arithmetic - 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 the tank if the tank is full how long will it take for the leakage alone to empty the - skillgun

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.