question_answer

Two taps A and B can fill a cistern in 15 min and 20 min respectively. Then both are turned on at the same time. If the tap A is turned off after some time, after that cistern is filled in 12 min. After how much time tap A is closed?

A) \[4\frac{3}{5}\min \]

B) \[3\frac{3}{7}\min \]

C) \[5\frac{2}{5}\min \]

D) \[8\frac{1}{9}\min \]

E) \[7\frac{3}{4}\min \]