SOLUTION: John can wash and wax a car in 4 hours. Max can wash and wax a car in 5 hours. How long would it take them to do it together?

Question 441446: John can wash and wax a car in 4 hours. Max can wash and wax a car in 5 hours. How long would it take them to do it together?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
John can wash and wax a car in 4 hours. Max can wash and wax a car in 5 hours. How long would it take them to do it together?
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John's rate = 1/4 job/hr
Max's rate = 1/5 job/hr
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Together rate = 1/x job/hr
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Equation:
rate + rate = together rate
1/4 + 1/5 = 1/x
Multiply thru by 20x to get:
5x + 4x = 20
9x = 20
x = 20/9 = 2 2/9 hrs (time to do the job together)
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2 2/9 hrs = 2 hrs (2/9)60 minutes = 13 min 20 seconds
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Final Answer: 2 hrs 13 min 20 seconds
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Cheers,
Stan H.
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