Question

the rate of change is $ _ million per year.

Answer 1

The slope of the graph is the difference of y- values over the difference in x-values.

$Slope=\frac{\Delta y}{\Delta x}$

The diffrence in y- values is

$\Delta y=450-50=400$

and the difference in x-values is

$1999-1991=8$

Hence, the rate of change (or the slope ) of the graph is

$\text{slope = }\frac{400}{8}$$\text{slope}=\frac{\ 50}{yr}$

which is our answer!