Inez has a phone card. The graph shows the number of minutes that remain on her phone card after a certain number of days.

Question

A graph titled Phone Card Balance has Number of Days on the x-axis, and Number of Minutes Remaining on the y-axis. A line goes through points (2, 750) and (8, 450).

The slope of the line that represents the data is –50, and the y-intercept is 850. What do the slope and y-intercept represent in Inez’s situation?
The y-intercept indicates that the phone card started with 850 minutes. The slope indicates that 50 minutes were used per day.
The y-intercept indicates that the phone card started with 50 minutes. The slope indicates that 850 minutes were used per day.
The slope indicates that the phone card started with 850 minutes. The y-intercept indicates that 50 minutes were added per day.
The slope indicates that the phone card started with 50 minutes. The y-intercept indicates that 850 minutes were added per day.

Answer 1

The correct interpretation of the slope and y-intercept in Inez's situation is:

The y-intercept indicates that the phone card started with 850 minutes. The slope indicates that 50 minutes were used per day.

Here's the reasoning:

1. Y-Intercept (850 minutes): This value represents the initial amount of minutes on the phone card (i.e., the number of minutes remaining at day 0, before any days have passed).

2. Slope (-50 minutes): The slope of -50 means that for each day that passes, Inez uses 50 fewer minutes from her phone card. Thus, it indicates the rate at which minutes are being used.

Overall, the interpretation accurately reflects the context described in the problem.