Gathering real-world data is a great way to help novice algebraists make meaning of slope, x-intercepts, and y-intercepts. But it can be challenging to find real-world data with negative slopes and interesting x-intercepts.
Walk the Plank from NCTM's Illuminations has students exploring the linear relationship between distance from a scale and weight.
Teaching Tip: Because weight can be a sensitive topic, consider using heavy items like bowling balls, dumbbells, and sandbags that can be placed on the plank and moved back and forth, rather than students' weights.
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