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?

$A$ cistern has $3$ pipes $A, B$ and $C$. Pipes $A$ and $B$ can fill it in $3$ and $4$ hours respectively,and pipe $C$ can empty it in $1$ hour. If the pipes are opened at $3 \text{ pm}$,$4 \text{ pm}$,and $5 \text{ pm}$ respectively on the same day,at what time will the cistern be empty?

Two pipes can separately fill a tank in $20$ $hrs$ and $30$ $hrs$ respectively. Both the pipes are opened to fill the tank,but when the tank is $\frac{1}{3}$ full,a leak develops in the tank through which $\frac{1}{3}$ of the water supplied by both the pipes per hour leaks out. What is the total time (in $hrs$) taken to fill the tank?

An inlet pipe fills $\frac{1}{8}$ part of a tank in $1 \ h$. How much time (in $h$) will the pipe take to fill the empty tank?

$A$ water tank has two pipes. The empty tank is filled in $12$ $min$ by the $1$st pipe and the full tank is emptied by the $2$nd pipe in $20$ $min$. What is the time required to fill the $1/2$ full tank when both pipes are in action (in $min$)?

Two pipes can fill a tank in $10$ $hours$ and $12$ $hours,$ while a third pipe can empty the full tank in $20$ $hours.$ If all three pipes operate simultaneously,in how much time will the tank be filled?