SOLUTION: one man & 2 boys can do a piece of workin 12 days, which can also done by 3 men & 1 boy in 6 days. How long it would take for one alone man to complete the work?

Question 72642: one man & 2 boys can do a piece of workin 12 days, which can also done by 3 men & 1 boy in 6 days. How long it would take for one alone man to complete the work?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
one man & 2 boys can do a piece of workin 12 days, which can also done by 3 men & 1 boy in 6 days. How long it would take for one alone man to complete the work?
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I would appreciate seeing how your text or instructor does these problems.
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This is the best I can do with it:
(1m + 2b)(12 days) = 1 job
(3m + 1b)(6 days) = 1 job
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The 1st equation can be changed to read:
2(1m+2b)(12 days)(1/2) = 1 job
or
(2m+4b)(6 days) = 1 job
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Then you can see that 3m+1b = 2m+4b
Then 1m=3b
or b=(1/3)m
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Putting that into the 1st equation you can get:
(1m + 2(1/3)m)(12 days) = 1 job
[(5/3)m](12 days) = 1 job
Then: (3/5)[(5/3)m](12 days)(5/3)= 1 job
(1 m)(20 days) = 1 job
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So, 1 man can do the job in 20 days.
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Cheers,
Stan H.
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