One crew can seal a parking lot in 12 hours and another in 16 hours. How long will it take to seal the parking lot if the two crews work together?.
hr
unit rate of first crew = 1/12 parkinglots/hour
unit rate of 2nd crew = 1/16 pl/h
combined rate = (1/12 + 1/16) pl/h = 7/48 pl/hr
time = 1 pl/(7/48 pl/hr)
= 48/7 hours or 6.857 hours or 6 hours and appr 51 minutes