Question

To solve work problems, find the portion of the job each person completes in 1 unit of time. The sum of these portions is the portion of the job completed in 1 unit of time. You can mop a floor in 8 minutes. Your friend can mop the same floor in 12 minutes. Working together, how much time does it take to mop the floor?

Answer 1

4.8 minutes

Explanation:

Using the given hint, working together, the amount of floor mopped in 1 minute is ...

1/8 + 1/12 = 3/24 +2/24 = 5/24 . . . . jobs/minute

The reciprocal of that is the rate in terms of minutes per job. Thus the entire job takes 24/5 = 4.8 minutes.