SOLUTION: A man estimated that he could do a certain job in 12 hours. After he had worked alone for 4 hours, he hired an assistant to help him, and together the completed the job in an addi

Question 800614: A man estimated that he could do a certain job in 12 hours. After he had worked alone for 4 hours, he hired an assistant to help him, and together the completed the job in an additional 5 hours. how long would the assistant have needed to do the job alone?
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
A man estimated that he could do a certain job in 12 hours. After he had worked alone for 4 hours, he hired an assistant to help him, and together the completed the job in an additional 5 hours. how long would the assistant have needed to do the job alone?
***
12 hrs=man could do the job alone
1/12=his work rate
let x=hrs assistant could do the job alone
1/x=his work rate
..
man worked 9 hrs
assistant worked 5 hrs
9/12+5/x=100% of job
9/12+5/x=1
9x+60=12x
3x=60
x=20
time assistant could do the job alone=20 hrs
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