SOLUTION: Kevin paints a house in 8 hours. Josh paints a house in 10 hours. Working together, how fast can they get the job done? 1/8 + 1/10 = 1/x 1*(10) + 1*(8) = 18/(10*8) 80/1

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Question 812029: Kevin paints a house in 8 hours. Josh paints a house in 10 hours. Working together, how fast can they get the job done?
1/8 + 1/10 = 1/x
1*(10) + 1*(8) = 18/(10*8)
80/18= 4.44444

I found 4.44 hours, but I'm not confident in my answer.
Found 2 solutions by Alan3354, richwmiller:
Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website!
Kevin paints a house in 8 hours. Josh paints a house in 10 hours. Working together, how fast can they get the job done?
1/8 + 1/10 = 1/x
1*(10) + 1*(8) = 18/(10*8)
80/18= 4.44444

I found 4.44 hours, but I'm not confident in my answer.
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Why not? If each of them took 10 hours, it'd be 5.
If each took 8 hours, it'd be 4.
So 8 and 10 --> between 4 & 5 hours.
80/18 is correct.
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A shortcut is product/sum --> 80/18

Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website!
Let's think about the problem to see if your answer is reasonably within range.
Kevin can paint the house alone in 8 hours. Josh is a little slower.
If they both could do it in 9 hours alone they should finish the job together in 4.5 hours.
You came up with 4.44 hours which is pretty close. So it is a reasonable answer within range.
It is 4.44 hours.