Question

An illustration shows the first quadrant of a coordinate plane titled Population of a City Since 1900.
The x-axis shows years since 1900 and ranges from 0 to 80 in increments of 10. The y-axis shows population per thousand and ranges from 0 to 80 in increments of 5. Nine points are plotted on the graph. The points are plotted at approximate coordinates (0, 20), (10, 28), (20, 30), (30, 35), (40, 47), (50, 55), (60, 57), (70, 68), and (80, 66). An upward slanting line starts at (0, 20) and continues to (60, 57).
The population growth of a city since 1900 is represented by a linear model. Interpret the slope and the y-intercept.
A. For every year since 1900, the population grew by approximately 300. In 1900, the population was 0.
B. For every 0.65 of a year since 1900, the population grew by approximately 1,000. In 1900, the population was 20,000.
C. For every year since 1900, the population grew by approximately 650. In 1900, the population was 20,000.
D. For every year since 1900, the population grew by approximately 1,590. in 1900, the population was 20,000.

Answer 1

C.

Using the line from (0, 20) to (60, 57), slope = (57 − 20)/(60 − 0) = 37/60 ≈ 0.6167 thousand people per year ≈ 617 people/year (≈650 people/year as in option C). The y‑intercept 20 means the population in 1900 was 20 thousand.