$A$ 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?

$A$ cistern has two taps which fill it in $12$ $minutes$ and $15$ $minutes$ respectively. There is also a waste pipe in the cistern. When all the pipes are opened,the empty cistern is filled in $20$ $minutes$. How long will the waste pipe take to empty a full cistern?

$2$ pipes $A$ and $B$ can fill a tank separately in $60$ $min$ and $70$ $min$ respectively. There is a third pipe attached to the bottom of the tank to empty it. The tank is filled in $60$ $min$ when all three pipes are opened. In how much time $(min)$ will the third pipe alone take to empty the tank?

$A$ cylindrical tank of diameter $25 \ cm$ is full of water. If $11 \ litres$ of water is drawn off,the water level in the tank will drop by (Use $\pi = 22/7$)?

Pipe $A$ can fill a cistern in $6 \, h$ and pipe $B$ can fill it in $8 \, h$. Both the pipes are opened simultaneously,but after $2 \, h$ pipe $A$ is closed. How many hours will $B$ take to fill the remaining part of the cistern?

Three pipes $A, B$ and $C$ can fill a tank from empty to full in $30$ minutes,$20$ minutes and $10$ minutes respectively. When the tank is empty,all the three pipes are opened. $A, B$ and $C$ discharge chemical solutions $P, Q$ and $R$ respectively. What is the proportion of solution $R$ in the liquid in the tank after $3$ minutes?