Clip 11/16: Adding and Subtracting Fractions Using a Line Plot Lesson Part 2C

Overview

Mallory gathers her students back to the carpet as a whole group, so that they can all see “some different models coming up.” She asks “Can someone talk to me about how they figured out what fractional parts were greater than one?” She records one student’s description of how he knew what to combine with the amounts greater than one, and asks the group, “Where did your eyes tend to go when you’re looking at fractions that are greater than one? How did you know that one and one-eighth was greater than one?”

Mallory also asks a group to share an error that they noticed in their work. The student shares that “We made the mistake of thinking those three whole pounds instead of two.” Mallory suggests to the whole group that they “check off the amounts as you add them, to keep your thoughts organized.” She shares two ways of solving the problem, and the students observe that both are correct; Mallory discusses the strengths of each approach: “Angel’s Way” and her way.

Teacher Commentary

I'm so happy that came out. That was, like, exactly what I wanted to be revealed. With fractions, there's so many parts that if you try to teach from a book, or if you try to teach without allowing any play with it or conversation or dialogue, it really doesn't do it justice. These students’ models showed different choices, shading in separately, which they're comfortable with what three-fourths looks like. And they know what repeated addition looks like. So on average, they can combine those together, but then to allow them to realize, well, there's other ways you can then put it to a part of a whole to show twelve for us. And in that there's three completely shaded sections of it, just—it can go on forever. That's why I love this. You only need one problem. One problem can get you all of these different elements!