<PRE><B>Question 268393</B>
    George can do a certain job in 70 minutes while Abe can do the same job in 30 minutes. How long would it take the two workers to do the job if they work together?
.
Let x = time (in minutes) for both to do the job together
then
x(1/70 + 1/30) = 1
Multiplying both sides by (70)(30) we get:
x(30 + 70) = (70)(30)
100x = (70)(30)
x = (70)(30)/100
x = 21 minutes
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