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A teacher in our district is deducting points from her students' inequality graphs such as x>1 if the student does not darken the number line all the way to the end of the arrow that is drawn on the given number line. I have always allowed my students to draw a darkened arrow that points in the correct direction but have allowed their arrows to either be shorter than the given number line or even longer than the given number line. Her argument for deducting points is that every book shows the arrow ending exactly where the number line arrow ends. I have not found any books that aren't as she says. My argument is that the number line is a portion of the cartesian coordinate plane and has no end, so as long as the arrow is pointing in the correct direction, it indicates that the line continues in that direction and is a correct solution. Have I been wrong all of these years?
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