Pipes - Cistern

6 )

A tank has three pipes. The first pipe can fill 1/2part of the tank in 1 hour and the second pipe can fill 1/3 part in 1 hour. The third pipe is for making the tank empty. When all the three pipes are open, 7/12th part of the tank is filled in 1 hours. How much times will the third pipe take to empty the completely filled tank?

7 )

Two taps can separately fill a tank in 12 min and 15 min. The first tap was replaced with a tap of double the radius and the second tap was replaced with a tap of half the radius. Now in what time will the tank get filled?

8 )

A bath can be filled by the cold water pipe in 20 minutes and by the hot water pipe in 30 minutes. A person leaves the bathroom after turning on both pipes simultaneously and returns at the moment when the bath should be full. Finding, however, that the waste pipe has been open, he now closes it. In 6 minutes more the bath is full. In what time would the waste pipe empty it?

9 )

A water tank can be filled by a tap in 30 minutes and another tap can fill it in 60 minutes. If both the taps are kept open for 5 minutes and then the first tap is closed, how long will it take for the tap to fill the remaining part of the tank?

10 )

Pipe A can fill a tank in 36 minutes and pipe B can fill it in 45 minutes. If both the pipes are opened to fill an empty tank, in how many minutes will it be full?