Q.28 :-Tap A can fill a tank in 60 minutes while tank B can fill it in 90 minute. The opening at the bottom can empty the full tank in 3 hours. When the
tank was empty both the taps were opened to fill the tank. After 15 minutes it was detected that the opening at the bottom was left unblocked and
immediately it was closed. After how much more time was the tank completely filled ?
24 minutes
27 minutes
21 minutes
30 minutes​