<PRE><B>Question 521566</B>
David can paint the outside of a house in 12 hr. Bill can paint the same house in 9 hr. How long will it take them working together to paint the house?
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David rate = 1/12 job/hr
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Bill rate = 1/9 job/hr
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Together rate = 1/x job/hr
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Equation:
rate + rate = together rate
1/12 + 1/9 = 1/x
9x + 12x = 9*12
21x = 9*12
7x = 9*4
x = 36/7 is approximately = 5 hrs 9 minutes
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Cheers,
Stan H.
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