SOLUTION: One crew can seal a parking lot in 15 hours and another in 20 hours. How long will it take to seal the parking lot if the two crews work together?

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Question 783796: One crew can seal a parking lot in 15 hours and another in 20 hours. How long will it take to seal the parking lot if the two crews work together?
Answer by josgarithmetic(39628) About Me  (Show Source):
You can put this solution on YOUR website!
That question in other wording is, what is the combined rate of work for the two crews together?

Their rates would be additive, and you would use unit of job per hour.
1%2F15%2B1%2F20=%284%2F4%29%281%2F15%29%2B%283%2F3%29%281%2F20%29=7%2F60

Now if you want as HOURS per JOB, then find the reciprocal:
60%2F7 HOURS per JOB
highlight%288%264%2F7%29 Hours per Job.