Three pipes $A, B$ and $C$ can fill a cistern in $6$ $hrs$. After working together for $2$ $hrs$,$C$ is closed and $A$ and $B$ fill the remaining part of the cistern in $8$ $hrs$. Find the time (in $hrs$) in which the cistern can be filled by pipe $C$ alone.

An empty tank can be filled by pipe $A$ in $4$ $h$ and by pipe $B$ in $6$ $h$. If the two pipes are opened for $1$ $h$ each alternately,starting with pipe $A$,then in how much time will the tank be filled?

In what time would a cistern be filled by three pipes whose diameters are $1 \text{ cm}$,$1 \frac{1}{3} \text{ cm}$,and $2 \text{ cm}$,running together,when the largest alone will fill it in $61 \text{ minutes}$,the amount of water flowing in by each pipe being proportional to the square of its diameter? (in $\text{minutes}$)

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

Three pipes $A, B$ and $C$ can fill a tank in $30 \ min$,$20 \ min$ and $10 \ min$,respectively. When the tank is empty,all the three pipes are opened. If $A, B$ and $C$ discharge chemical solutions $P, Q$ and $R$ respectively,then the part of solution $R$ in the liquid in the tank after $3 \ min$ is

Two pipes can fill a tank in $15$ $hours$ and $12$ $hours$ respectively,while a third pipe can empty it in $20$ $hours$. If the tank is empty and all three pipes are opened together,then in how much time will it take to fill the tank completely?