## Precalculus (6th Edition)

average rate of change in $[2009, 2013] =1,320.5$ thousands per year The number new of motor vehicles sold in the United States increased at an average of $1,320.5$ thousands per year from 2009 to 2013.
RECALL: The average rate of change of a function in the interval $[a,b]$ is given by the formula: average rate of change$=\dfrac{f(b)-f(a)}{b-a}$ The given graph shows that: $f(2009)=10,602$ $f(2013)=15,884$ Use the formula to obtain: average rate of change in $[2009, 2013]$ = $\dfrac{15884-10602}{2013-2009} \\=\dfrac{5282}{4}$ $\\=1,320.5$ thousands Thus, the number new of motor vehicles sold in the United States increased at an average of $1,320.5$ thousands per year from 2009 to 2013.