Pipes A and B can fill a tank in$12 \mathrm{hours}$ and $16 \mathrm{hours}$ respectively and pipe C can empty the full tank in $24 \mathrm{hours}$. All three pipes are opened together, but after $4 \mathrm{hours}$ pipe A is closed. In how many hours from the beginning the tank be filled?

Of the three pipes, the first two can fill an empty tank in 10.8 and 21.6 hours respectively, while the third pipe can empty the tank in 18 hours. If the tank is empty and all the three pipes are opened together then in how many hours will tank fill?

Pipe A in comparison to pipe B fills a tank in one fourth time. Pipe C in comparison to pipe A takes 3 times more time to fill the tank. If the three pipes are opened together, the tank is filled in 24 hours. If Pipe C is not opened, how much time will it take to fill the tank?

Two pipes separately take $5$ hours and $8$ hours respectively to fill a tank. The third pipe takes $3.2$ hours to drain out the water from the tank. How much time will all the three pipes take to fill the completely empty tank?