<PRE><B>Question 51346</B>
Batman can clean up all of the crime in Gotham city in 8hr working alone. Robin can do the same job alone in 12hr. If Robin starts crime fighting at 8 A.M and Batman joins him at 10 A.M, then at what time will they have all of the crime cleaned up??
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Batman DATA:
time = 8 hr/job ; rate = 1/8 job/hr
Robin DATA:
time= 12 hr/job ; rate = 1/12 job/hr

EQUATION:
Robin work plus Together work = 1 job
2hr(1/12)job/hr+xhr.(1/8+1/12)job/hr = 1 job
(1/6)+x(20/96)=1
16+20x=96
20x=80
x=4 hrs.
They will be finished at 10 A.M. + 4 hours = 2:00PM

cheers,
Stan H. 


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