Question 1153557
Mark's rate of work = 1/2 job per hour
Rachel's rate of work = 1/3 job per hour
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Rate working together = 1/2 + 1/3 = 5/6 job per hour
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Since they can complete 5/6 of the job per hour working together, this means it will take them 6/5 hours to complete the job.  6/5 hours is 1.2 hours.  1.2 hours is <b>1 hour and 12 minutes</b>.  (Every 0.1 hour is 6 minutes.)