The slope of a line that passes through points (x1, y1) and (x2, y2) is given by:
[tex]m=\frac{y_2-y_1}{x_2-x_1}\text{.}[/tex]
The slope gives us the rate of change of a linear function. From the graph, we see that the line passes through points:
[tex]\begin{gathered} (x_1,y_1)=(1991,250), \\ (x_2,y_2)=(1995,270). \end{gathered}[/tex]
Replacing these values in the equation above, we get:
[tex]m=\frac{270-250}{1995-1991}=\frac{20}{4}=5.[/tex]
Answer
The population is growing by 5 million people per year.
