Question

An empty swimming pool can be filled to capacity through an inlet pipe in 3 hours, and it can be completely drained by a drain pipe in 6 hours. if both pipes are fully open at the same time, in how many hours will the empty pool be filled to capacity?

Answer 1

Solution :-

In 3 hours the swimming pool can be filled to the capacity.

Then, in 1 hour the part of swimming pool can be filled = 1/3th part

And, 

In 6 hours, the drain pipe completely drain the swimming pool 

Then, in 1 hour, the drain pipe will completely drain the part of the swimming pool =

1/6th part

When both pipes are open,

⇒ 1/3 - 1/6 = 1/6

So, 1/6th of the swimming pool is filled in 1 hour.

Hence it will take 6 hours to completely fill the pool to capacity.

Answer.

Answer 2

Answer:

Time taken by inlet pipe to fill = 3 hours

Volume filled in 1 hour =

Time taken by outlet pipe to empty = 6 hours

Volume emptied in 1 hour =

Amount of work done in an hour =

Therefore time taken (flipping the numerator and denominator) = 6 hours