Question

A vessel can be filled by a pipe in 25 minutes and ut can be emptied by a waste pipe in 20 minutes .if both the pipes be opened when the vessel is full how soon will it be empty

Answer 1

Part filled by pipe A in 1 min = 1/25

Part emptied by pipe B in 1 min = 1/20

Vessel will be empty in = 1/25 - 1/20 = 4-5/100 = -1/100 ( - sign indicates that vessel will be drained fast than getting filled)

So it will get empty in 100 mins = 1 hour 40 mins completely