SOLUTION: if bob has a hose and a swimming pool it takes 3 hours to fill the pool and it takes 5 hours to empty it with the drain open. If bob leaves the drain open and the hose on how long

Question 283900: if bob has a hose and a swimming pool it takes 3 hours to fill the pool and it takes 5 hours to empty it with the drain open. If bob leaves the drain open and the hose on how long will it take to fill the pool?
Found 2 solutions by richwmiller, solver91311:
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
This belongs under rate of work, painting and pool filling.
Look for some example in that category. There have been several in the last few days.
You can see now why it is important to use the right category.
I will set it up since John's way is much too complicated.
x/3-x/5=1
5x-3x=15
2x=15
x=7.5 hours

Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

A typical "working together" problem works out like this:

If A can do a job in x time periods, then A can do of the job in 1 time period. Likewise, if B can do the same job in y time periods, then B can do of the job in 1 time period.

So, working together, they can do

of the job in 1 time period.

Therefore, they can do the whole job in:

time periods.

But in your case, you have A doing work and B UNdoing work, so you need to calculate:

And then:

John

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