The percentage of battery remaining after a certain number of hours after a cellphone is turned on can be represented by the graph shown.

Question

Graph with x axis labeled number of hours and y axis labeled percent of battery remaining, with line that passes through the points 0 comma 100 and 2 comma 60 and 4 comma 20.

Part A: Write an equation in slope-intercept form to describe the relationship in the graph. (2 points)

Part B: Explain how you determined the equation. (1 point)

Part C: What is the meaning of the slope in the given situation? (1 point)

Answer 1

Part A: The equation in slope-intercept form is y = -20x + 100.

Part B: The equation was determined by observing the points (0,100), (2,60), and (4,20) on the graph. The slope is found by calculating the change in y-values over the change in x-values, which is (-40)/(4-0) = -20. The y-intercept can be found by observing that at x=0, y=100.

Part C: The slope of -20 indicates that the battery percentage decreases by 20% every hour. This means that the battery is depleting at a constant rate.