Pipes and Cisterns

Pipe $A$ can fill one fourth of a tank in $5$ hours and pipe $B$ can empty the full tank in $30$ hours.If both pipes are opened simultaneously, then in how many hours will the empty tank be filled.

Two pipes P and Q would fill an empty cistern in $24$ minutes and $32$ minutes respectively . Both the pipes being opened together , find when the first pipe must be turned off so that the total time taken to fill the empty cistern is $28$ minutes.

Two taps can separately fill a cistern in $10$ minutes and $15$ minutes, respectively and when the waste pipe is open, they can together fill it in $18$ minutes. The waste pipe can empty the full cistern in:

A tank can be filled by two pipes A and B separately in 3 hours and 3 hours 45 minutes respectively, A third pipe C can empty the full tank in 1 hour, when the tank was exactly half-filled, all the three pipes are opened. The tank will become empty in

If two pipes are put in operation simultaneously, the tank is filled in $24$ min. One pipe fills the tank $20$ min faster than the other. How many hours does the faster pipe take to fill the tank ?

A cistern which could be filled in $9$ hours takes one hour more to be filled owing to a leak in its bottom. If the cistern is full, in what time will the leak empty it ?

Pipes, $A, B$ and $C$ are attached to a cistern $A$ and $B$ can fill it in $20$ min and $30$ respectively, while $C$ can empty it in $15$ min $H A, B$ and $C$ kept in operation successively for $1$ minute each, how soon will the cistern be filled?

Two pipes A and B can fill a cistern in $30$ min and $40$ min respectively, Both the pipes are turned on simultaneously. When should the second pipe be closed if the cistern is to be filled in $24$ min ?

Two pipes $A$ and $B$ can fill a cistern is $12$ minutes and $15$ minutes respectively, but a third pipe $C$ can empty the full tank in $6$ minutes. $A$ and $B$ are kept open for $5$ minutes in the beginning and then $C$ is also opened. In what time will the cistern be emptied ?

A tap can fill a bath in $20$ minutes and another tap can fill it in $30$ minutes. Amit opens both the taps simultaneously. When the bath should have been full, he finds that the waste pipe was open. He then closes the waste pipe and in another $4$ minutes the bath is full. In what time would the waste pipe empty it ?

Three pipes A, B and C can fill a tank in 6 min, 8 min, and 12 min. respectively. The pipe C is closed for 4 min before the tank is filled. In what time would the tank be fill ?