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Content Extension: Exploring Intersecting Lines in Context

We have spent some time with the concept of parallel slopes. However, not all situations result in parallel lines. What if we came across two lines that weren't growing at an equal rate?


Check out the next clip from "Hikers Beware" in which a group of students presents its work to the class. We're not so much interested in what they're saying, but rather what is on their poster. In particular, take a good, long look at what the lines on their poster are doing.

Did you catch it? The lines weren't parallel after all-- they intersected! Although this lesson doesn't specifically address the intersection of lines, it is worthwhile for us as math teachers to talk about this topic. How would you have pointed this out to students? Why is it important for students to understand when lines intersect?