joe drives 360 miles at 60 miles per hour , and then he drives the next 120 miles at 40 miles per hour . what is his average speed for the entire trip in miles per hour ?
t 1 = 360 / 60 = 6 hours t 2 = 120 / 40 = 3 hours t = t 1 + t 2 = 9 hours avg speed = total distance / t = 480 / 9 = 53 mph = b
divide(add(360, 120), add(divide(360, 60), divide(120, 40)))