Question

alaina wants to decide whether her current cell phone plan is better than a package that another company offers. to compare the two plans, she plotted two lines on a graph, where \\(y\\) represented the total cost of one months service and \\(x\\) represented the megabytes of data that she used in a month. which part of the graph will represent the cost per megabyte of data used in each plan?

• the \\(x\\)-intercepts of the two lines
• the \\(y\\)-intercepts of the two lines.
• the slopes of the two lines.
• the coordinates of a point of intersection.

Explanation:

Identify variables and units

Using the Linear Functions knowledge point

$$
LATEXBLOCK0
$$

Determine the meaning of cost per megabyte

Using the Rate of Change knowledge point

$$ \text{Unit of cost per megabyte} = \frac{\text{Change in } y}{\text{Change in } x} = \frac{\text{Dollars}}{\text{Megabyte}} $$

Relate rate of change to graphical features

Using the Rate of Change and Linear Functions knowledge points

$$ \text{Rate of change} = \text{Slope of the line} $$

Answer:

• The x-intercepts of the two lines
• The y-intercepts of the two lines.
• The slopes of the two lines. (Correct answer)
• The coordinates of a point of intersection.