Pipes $P$ and $Q$ can fill a tank in $5$ and $6 \, h$, respectively, and pipe $C$ can empty it in $3 \, h$. If all the three are opened at $7 \, am$, at what time will two-fifths of the tank be filled?

Two pipes,$A$ and $B,$ can separately fill a cistern in $15$ $minutes$ and $18$ $minutes,$ respectively,while a third pipe $C$ can empty it in $6$ $minutes.$ Two pipes,$A$ and $B,$ are kept open for $6$ $minutes$ in the beginning and,then the third pipe is also opened. In what time (in $minutes$) will the cistern be emptied?

$A$ tank can be filled by one tap in $20$ $min$ and by another tap in $60$ $min$. Both the taps are kept open for $5$ $min$ and then the $1$st tap is shut off. After this,how much more time (in $min$) will it take for the tank to be completely filled?

An outlet pipe can empty a cistern in $3$ $h$. In what time (in $h$) will the pipe empty two-third part of the cistern?

$A$ water tank has two taps $A$ and $B$. Tap $A$ can fill it in $6$ hours,and tap $B$ can empty it in $5$ hours. If both taps are opened simultaneously,how much time (in hours) is required to empty the tank?

Two pipes can fill an empty tank separately in $24$ $minutes$ and $40$ $minutes$ respectively,and a third pipe can empty $30$ $gallons$ of water per $minute$. If all three pipes are opened,the empty tank becomes full in one $hour$. The capacity of the tank (in $gallons$) is: