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Question 698556: A father can do a job in a certain cumber of hours. His son takes twice as long as to do the job. Working together, they can do the job in 6 hours. How many hours does it take the father to do the job alone?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! A father can do a job in a certain cumber of hours. His son takes twice as long as to do the job. Working together, they can do the job in 6 hours. How many hours does it take the father to do the job alone?
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The father works as fast as 2 sons, equal to 3 sons taking 6 hours
--> each son takes 18 hours
--> father takes 9 hours.
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The hard way:
The son takes x hours alone
--> the son does 1/x of the job per hour
The father does 2/x per hour
Together, they do 1/x + 2/x per hour = 1/6
1/x + 2/x = 1/6
1 + 2 = x/6
x/6 = 3
x = 18 hours for the son
--> 9 hours for the father
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