$A$ cylindrical tank of diameter $25 \ cm$ is full of water. If $11 \ litres$ of water is drawn off,the water level in the tank will drop by (Use $\pi = 22/7$)?

One tap can fill a cistern in $2$ $hours$ and another can empty the cistern in $3$ $hours.$ How long will they take to fill the cistern if both the taps are opened?

$A$ tap can fill the cistern in $8$ hours and another can empty it in $16$ hours. If both the taps are opened simultaneously,the time (in hours) to fill the tank is?

Two pipes $A$ and $B$ can fill a tank in $15$ hours and $20$ hours respectively,while a third pipe $C$ can empty the full tank in $25$ hours. All three pipes are opened in the beginning. After $10$ hours,pipe $C$ is closed. Find the total time (in hours) in which the tank will be full.

Two pipes $A$ and $B$ can fill a cistern in $3$ $hours$ and $5$ $hours,$ respectively. Pipe $C$ can empty it in $2$ $hours.$ If all the three pipes are open,in how many $hours$ will the cistern be full?

If a pipe fills a tank in $6 \ h$,then what part of the tank will the pipe fill in $1 \ h$?