+1050 If Mark drives for 4 hours at 60 miles per hour and then drives another 5 hours at 80 miles per hour, what is his average speed, in miles per hour, for the trip?
+36917 AVERAGE speed = total distance / total time
total time = 4 = 5 = 9 hrs
then remember rate * time = distance
60 mi/hr * 4 hr = 240 mi
80 mi/hr * 5 hr = 400 mi total distance = 640 mi
AVERAGE speed = 640 mi / 9 hr = 71 . 11 mph ( 71 1/9 mph)
