Question 379651
Joan can shovel a certain driveway in 50 minutes.  If mary can shovel the same driveway in 20 minutes, how long will it take them, to the nearest minute, to shove the driveway if they work together?
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Let x = time (minutes) it takes for both
then
x(1/50 + 1/20) = 1
multiplying both sides by 1000:
x(20 + 50) = 1000
x(70) = 1000
x = 14.29
rounded:
x = 14 minutes