I intuitively understand the examples below, but I don't see an "average" in the average rate of change (I see a ratio of two delta values). What is the relationship between the average (arithmetic mean) and the average rate of change?
2+3+4 / 3 = 3 (arithmetic mean)
4 miles - 2 miles / 2 hours - 1 hour = 2 miles per hour (average rate of change)