SOLUTION: Zach can paint a house in 20 hours; Tommy can paint a house in 12 hours; and Ben can paint a house in 15 hours. How long will it take them to paint a house if all three work togeth

Question 748102: Zach can paint a house in 20 hours; Tommy can paint a house in 12 hours; and Ben can paint a house in 15 hours. How long will it take them to paint a house if all three work together?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Zach can paint a house in 20 hours; Tommy can paint a house in 12 hours; and Ben can paint a house in 15 hours. How long will it take them to paint a house if all three work together?
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rate + rate + rate = together rate
1/20 + 1/12 + 1/15 = 1/x
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6x + 10x + 8x = 120
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24x = 120
x = 5 hrs (time to do the job together)
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Cheers,
Stan H.
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