$A$ pipe $P$ can fill a tank in $12$ $min$ and another pipe $R$ can fill it in $15$ $min.$ But,the $3$rd pipe $M$ can empty it in $6$ $min.$ The $1$st two pipes $P$ and $R$ are kept open for $5$ $min$ in the beginning and then the $3$rd pipe is also opened. In what time (in minutes) is the tank emptied?

Pipes $A$ and $B$ can fill a tank in $5$ $hours$ and $6$ $hours$ respectively. Pipe $C$ can empty it in $12$ $hours.$ If all the three pipes are opened together,then the tank will be filled in

One tap can fill a cistern in $2$ hours and another can empty the cistern in $3$ hours. How long will it take to fill the cistern if both the taps are opened (in $\text{hours}$)?

$A$ water tank has three taps $A, B, C$. Tap $A$,when opened,can fill the water tank alone in $4$ hours. Tap $B$,when opened,can fill the water tank alone in $6$ hours,and tap $C$,when opened,can empty the water tank alone in $3$ hours. If taps $A, B,$ and $C$ are opened simultaneously,how long (in hours) will it take to fill the tank completely?

$A$ tap can fill a 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?

An oil drum can be filled with oil in $40$ $min$ by a filling pipe. Another outlet pipe can empty the entire drum in $60$ $min$. The outlet pipe was opened when $\frac{2}{3}$ part of the drum was filled with oil and closed after $15$ $min$. What time will it take to fill the drum when the filling pipe is opened now?