Pipes and Cistern - General Questions

Pipes A and B can fill a tank in 22 and 25 minutes, and pipe C can empty it in 17 minutes. If all three are opened together, how long will it take to fill the tank?

A pipe can fill a tank in 3 hours and another pipe can empty it in 22 hours. If both are opened together, in how much time will the tank be filled?

Two pipes A and B can fill a tank in 21 hours and 18 hours respectively. If both are opened together, how long will they take to fill the tank?

Pipes A and B can fill a tank in 28 and 18 minutes, and pipe C can empty it in 15 minutes. If all three are opened together, how long will it take to fill the tank?

Pipes A and B can fill a tank in 13 and 21 minutes, and pipe C can empty it in 40 minutes. If all three are opened together, how long will it take to fill the tank?