You leave your home at noon hoping to get to your destination, which is 300 miles away, by 5 p.m. During the first two hours of your trip you encounter road construction and only average 40 mph. What average speed do you need to maintain for the rest of your journey to get there on time?
distance covered in first two hours = 40 mph x 2 = 80 miles
distance to be covered in the remaining three hours = 400 - 80 = 320 miles
average speed for remaining three hours = 320 / 3 = 106.667 mph