A tap can fill a tank in 16 minutes and another can empty

A tap can fill a tank in 16 minutes and another can empty it in 8 minutes. If the tank is already half full and both the taps are opened together, the tank will be ?

1. Filled in 12 min.
2. Emptied in 12 min.
3. Filled in 8 min.
4. Emptied in 8 min.

Part emptied in 1 min. = (1/8 - 1/16) = 1/16
∴ Time taken to empty the full tank = 16 min.
Hence, time taken to empty the half tank = 8 min.