According to the U.S. census, the population of the city of Grand Rapids, MI, was 181,843 in 1980; 189,126 in 1990; and 197,800 in 2000.

Just like we can find the average velocity of a moving body by computing change in position over change in time, we can compute the average rate of change of any function f.f. In particular, the average rate of change of a function ff over an interval [a,b][a,b] is the quotient

f(b)- f (a)

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b - a