An international calling plan charges 45 cents per minute or fraction of a minute for each call. Which graph models the cost, y , in cents of making x minutes of international calls?
Answer
A
Image with description On a coordinate plane, the x axis is labeled as minutes and the y axis is labeled as cost. The x axis ranges from 0 to 10 in increments of 1. The y axis ranges from negative 0 to 54 in increments of 1 with a line break. The graph has 10 stepwise arrangements starting from (0 comma 45). Each step has an open circle, a line segment, and a closed circle, and all are connected. The first step begins at (0 comma 45) with a closed circle and ends at (1 comma 45) with an open circle. Each step goes from left to right. The last step has a closed circle at (9 comma 54) and an open circle at (10 comma 54).
B
Image with description Coordinate plane with x- and y-axes labeled. The x-axis is labeled Minutes and marked from 1 to 8. The y-axis is labeled Cost and marked at 45, 90, 135, 180, 225, 270, 315, 360, 405, and 450. A step graph is shown. Open circles are plotted at (0 comma 45), (1 comma 90), (2 comma 135), (3 comma 180), (4 comma 225), (5 comma 270), (6 comma 315), (7 comma 360), (8 comma 405), and (9 comma 450). Closed circles are plotted one unit to the right at the same y-values. Horizontal segments connect each open circle to the closed circle at the same height.
C
Image with description Coordinate plane with x- and y-axes labeled. The x-axis is labeled Minutes and marked from 1 to 8. The y-axis is labeled Cost and marked at 45, 90, 135, 180, 225, 270, 315, 360, 405, and 450. A step graph is shown. Closed circles are plotted at (0 comma 45), (1 comma 90), (2 comma 135), (3 comma 180), (4 comma 225), (5 comma 270), (6 comma 315), (7 comma 360), (8 comma 405), and (9 comma 450). Open circles are plotted one unit to the right at the same y-values. Horizontal segments connect each closed circle to the open circle at the same height.
D
Image with description On a coordinate plane, the x axis is labeled as minutes and the y axis is labeled as cost. The x axis ranges from 0 to 10 in increments of 1. The y axis ranges from negative 0 to 54 in increments of 1 with a line break. The graph has 10 stepwise arrangements starting from (0 comma 45). Each step has an open circle, a line segment, and a closed circle, and all are connected. The first step begins at (0 comma 45) with an open circle and ends at (1 comma 45) with a closed circle. Each step goes from left to right. The last step has an open circle at (9 comma 54) and a closed circle at (10 comma 54).
Explanation
Each started minute costs 45 cents, so a call lasting more than 0 and up to 1 minute costs 45 cents; more than 1 and up to 2 minutes costs 90 cents, and so on. The cost stays constant over each interval and jumps at whole-minute marks. Choice B shows each step open at the left endpoint and closed at the right endpoint, matching the charge for a fraction of a minute.
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