A climber is on a hike. after 2 hours he is at an altitude of 400 feet. After 6 hours, he is at an altitude of 700 feet. What is the average rate of change?

Average rate of change =

(change in height during some time) / (length of time for the change).

Change in height = (700 feet - 400 feet) = 300 feet

Time for the change = (6 hours - 2 hours) = 4 hours

Average rate of change = (300 feet) / (4 hours) = 75 feet per hour