Jim was driving to an interview 72 mi away. On the first leg of the trop he drove an average of 30 mph through a long construction zone, but was able to drive 60 mph after passing through this area. If driving time for the trip was 1 1/2 hr, how long was he driving in the const. zone?

Question

Jim was driving to an interview 72 mi away.  On the first leg of the trop he drove an average of 30 mph through a long construction zone, but was able to drive 60 mph after passing through this area.  If driving time for the trip was 1 1/2 hr, how long was he driving in the const. zone?

drwls · Answer

Let the construction zone driving time be T hours. Then, 1.5 - T hours were spent driving at 60 mph. The total distance driven is 30*T + 60*(1.5 - T) = 72 miles 90 - 72 = 30 T T = 0.600 hours = 36 minutes