A cistern can be filled by a supply pipe in 30 min and emptied by a waste pipe in 4/5 hr. If both pipes are opened together, in what time will the cistern be filled?


This is reply by AI

Let the volume of cistern be V
Pipe fill cistern in 30 mins or 0.5 hours , so rate of water coming out = V/0.5
rate of water in pipe 1 = 2V

Similarly rate of water emptying = V/4/5 so 5V/4

If both pipes work together, Water will be simultaneously added and removed
so 2V - 5V/4 = 3V/4

So Water will be added by 3V/4 l/hr speed
V volume in the cistern will be filled in V/3V/4 = 4/3 hours

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