Question

The JayC dealership tracks its car sales based on the type of car. The graph shows the percent of sales that were Hybrid Electric Vehicles (HEV) for the years (2010–2015).

​Explain what year is represented by an x-value of 3 on the graph.

Write the equation of the line of best fit in the graph. Define your variables and include the units.

What does the slope of the line represent in this problem situation?

Answer 1

Explanation:

'3' on the horizontal axis represents the year 2013, which is 3 years AFTER 2010.

According to the graph, the vertical intercept is 26, which represents the percent of HEV sold in the year 2010. Thus, the vertical intercept is (0, 26). As we go from (0, 26) to (7.5, 0), x (the 'run') increases by 7.5 and y (the 'rise' decreases by 26. Thus the slope of this line is

rise

m = --------- = -26/7.5 = -3.47 percent/year

run

The desired equation is then:

y = -3.47 (percent/year)x

The slope of this line is the rate of change

percent

------------

year

and tells us that the percent of HEV sold is decreasing by -3.47 percent per year.