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?

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?

$A$ 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?

$A$ cistern is normally filled in $8$ $hours$,but it takes $2$ $hours$ longer to fill because of a leak at its bottom. If the cistern is full,the leak will empty it in (in $hours$):

$A$ big tanker can be filled by two pipes $A$ and $B$ in $60$ and $40$ $min$ respectively. What time will it take to fill an empty tanker if tap $B$ is used for half of the total time and both taps $A$ and $B$ together are used for the remaining half of the time?

$A$ tap having diameter $d$ can empty a tank in $40$ $min$. How long will another tap having diameter $2d$ take to empty the same tank (in $min$)?