A pipe can fill a tank in 20 minutes and another pipe can fill it in 30 minutes. A man opened both the pipes and left. He returned at that time when the tank should be filled completely but he noticed that the tank was not full due to a leakage. He repaired that leakage and after that the tank was filled in 4 minutes. In how much time will that leakage empty the tank?

36 min

The tank should be filled in = \(\frac{60}{5}\) = 12 min

Man return after 12 min. and after the repair tank filled in 4 min.

In last 4 min tank filled = 4 × 5 = 20 ltr

Remaining 40 ltr was filled earlier in 12 min by pipe A, B and a leakage.

Hence,

Efficiency of A + B + Leakage = \(\frac{40}{12}\) = \(\frac{10}{3}\)

Efficiency of Leakage = \(\frac{10}{3}\) - 5 = -\(\frac{5}{3}\)

Therefore,

Leakage can empty the tank in = \(\frac{60}{\frac{5}{3}}\) = 36 min.