$A$ tank is filled in $5$ $hours$ by three pipes $A, B$ and $C$. Pipe $C$ is twice as fast as $B,$ and $B$ is twice as fast as $A$. How much time (in $hours$) will pipe $A$ alone take to fill the tank?

Pipe $A$ can fill a tank in $30$ minutes,while pipe $B$ can fill the same tank in $10$ minutes and pipe $C$ can empty the full tank in $40$ minutes. If all the pipes are opened together,how much time will be needed to make the tank full?

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?

$A$ cistern has three pipes $A, B$ and $C$. Pipes $A$ and $B$ can fill it in $3 \, h$ and $4 \, h$, respectively, while pipe $C$ can empty the completely filled cistern in $1 \, h$. If pipes are opened in order at $3:00 \, pm$, $4:00 \, pm$ and $5:00 \, pm$, respectively, at what time will the cistern be empty?

Two taps $A$ and $B$ can fill an oil tank in $15$ $min$ and $18$ $min$ respectively,while a third tap is used to empty the tank. The third tap is opened after $6$ $min$ of opening of taps $A$ and $B$. If the tank empties in $16 \frac{1}{2}$ $min$ after opening the third tap,then in how much time (in $min$) can the third tap empty the full tank?

$A$ water tank is $\frac{2}{3}$ full. Pipe $A$ can fill the tank in $10$ $minutes$ and pipe $B$ can empty it in $6$ $minutes$. If both the pipes are open,how long will it take to empty the tank completely?