Question

Pipes A and B can fill an emply tank in 10 hours and 15 hours respectively. If both are opened together in
the emply tank, how much time will they take to fill it completely?
​

Answer 1

Answer:

Pipe A fills(positive work) in 10 hrs.

Pipe B empties(negative work) in 15 hrs.

Total work can be taken as LCM(10,15) that equals to 30

Since A filling in 10hrs ,hourly efficiency of A is +3 [ positive work]

and B filling in 15hrs, hourly efficiency of B is -2 [ negative work]

Total hourly efficiency of A and B together equals to 1 .

So if both pipes are opened, the tank will be filled in 30 hours.