The graph shows the total distance Sam drove from 6 a.m to 11 a.m. How many miles per hour is the car's average speed for the period from 6 a.m. to 11 a.m.?

Average speed = total distance traveled/total time it took.

The trip took 5 hours in total and they travelled 160 miles, giving you an average speed of 160/5 = 32 mph.