SOLUTION: Bobo can wash the car in 36 minutes by himself. When his brother Otto helps, they finish in 20 minutes. How long would it take Otto to wash the car by himself?

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Question 691553: Bobo can wash the car in 36 minutes by himself. When his brother Otto helps, they finish in 20 minutes. How long would it take Otto to wash the car by himself?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Bobo can wash the car in 36 minutes by himself. When his brother Otto helps, they finish in 20 minutes. How long would it take Otto to wash the car by himself?
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Bobo rate = 1/36 job/min
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Together rate = 1/20 job/min
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Otto rate = 1/x job/min
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Equation:
rate + rate = together rate
1/36 + 1/x = 1/20
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20x + 20*36 = 36x
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16x = 20*36
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4x = 5*36
x = 5*9
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x = 45 minutes (time for Otto to do the job alone)
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Cheers,
Stan H.