<PRE><B>Question 816035</B>
b = 1 job / 12 hrs
j = 1 job / 20 hrs
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work rate for both men:
r = b + j
r = 1/12 + 1/20
r = 20/12(20) + 12/12(20)
r = 20/240 + 12/240
r = 32/240 jobs/hr
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r = u / t
t = u / r
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t = u / r
t = 1 job / ( 32/240 jobs/hr)
t = 240 hr / 32 job
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Answer:
t = 7.5 hr/job
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