The teacher's role during this activity is to help students draw connections between what is happening on the track and what is happening on the graph. In the course of discussing the guiding questions, students can become more precise in reasoning quantitatively about the relationships. For example, by inspecting the track, the graph, and the table, students may discuss any of the following topics. The length of the boy's stride is 2, so you know his distance by multiplying the time by 2. Students can relate the runner's trips proportionally- by changing the stride the runner may travel twice as far in the same amount of time.
Students can begin to describe rate of change informally by inspecting the slope of the line.
The closing should be structured so that students can review and pull together what they have learned. Include questions or tasks that encourage students to reflect on their work. For example, you could have students consider questions similar to the guiding questions used above or consider those examples written below after they have finished the activity. In so doing they will consolidate what they have learned. Furthermore, this will provide an opportunity for you and the students to assess what they have learned and what they still want or need to understand.