Question 156779
Jack does 1/5 job in 1 hr.
Mary does 1/7 job in 1 hr.
1/5 + 1/7
=7/35 + 5/35 = 12/35 of job is done in 1 hr together
35/12 hrs it takes them both to do the job or 2 hrs 11/12 hrs or 2 hrs 55 min.
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Ed