Two pipes $A$ and $B$ can fill a cistern in $37 \frac{1}{2}$ minutes and $45$ minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour,if pipe $B$ is turned off after how many minutes?

$A$ 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?

$2$ 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?

$A$ tap can fill the 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 empty pool being filled with water at a constant rate takes $8$ $hours$ to fill $\frac{3}{5}$ of its capacity. How much more time will it take to finish filling the pool?

$A$ tank is filled by three pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is filled by the third pipe alone. The second pipe fills the tank $5$ $hours$ faster than the first pipe and $4$ $hours$ slower than the third pipe. The time (in $hours$) required by the first pipe is: