<PRE><B>Question 156139</B>
Two teachers are grading math homework. 
One teacher can grade a stack of papers in 50 minutes: rate = 1/50 papers/minute
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the other can complete the job in 100 minutes: rate = 1/100 papers/minute
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Together rate = 1/50 + 1/100 = 3/100 papers/min
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How long doesit take them to grade all the papers if the first teacher grades alone for 23 minutes, then they work together to finish?
EQUATION:
rate*time = work done
(1/50)23 + x(3/100) = 1 job done
(46/100) + 3x/100 = 1
46 + 3x = 100
3x = 54
x = 18 minutes (time it will take to finish the job)
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Cheers,
Stan H.
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