A. 32 minutes
Feedback Let X hours be the time taken to fill a tank by P.
Let Y hours be the time taken to empty the tank by Q.
Then the time taken to fill the tank when P and Q are switched together : XY / Y-X hours.
Here, X = 16 minutes And Y = 32 minutes
Therefore required time = 16 x 32/(32 - 16) = 32 x 16 / 16 = 32 minutes.