Question 163802
One can do 1/2 the job in 1 hr, another 1/3 and another 1/4 the job in 1 hr.
1/2 + 1/3 + 1/4
=6/12 + 4/12 + 3/12
=13/12 of the job in 1 hr together
12/13 of an hour to do the job working together.
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Ed