This lesson is optional because it does not address any new mathematical content standards. This lesson does provide students with an opportunity to apply precursor skills of mathematical modeling (MP4). In previous lessons, students identified lines of symmetry in two-dimensional figures, identified figures with line symmetry, and drew figures with different numbers of lines of symmetry. In this lesson, students apply what they have learned about symmetry to consider how symmetry affects sports fields and courts. Students consider examples of baseball parks that are symmetrical and asymmetrical. Then they consider how changing a sports field with a line of symmetry would affect the game. In the last activity students design sports fields with no lines of symmetry and create rules for playing on the newly designed field.

Unlike talking, listening is a difficult thing to observe. At what points in the lesson did you observe students listening to one another’s ideas today in class? What indicators do you have that they were listening?