After going through the two main solution methods for the photo enlargement problem, the teacher asks the students how they can generalize.
Definition of Proportionality, Photo Enlargement Problem, Clip 2, 3:36
This is a follow up to previous clip, an example of the teacher asking questions of the groups to help them think about photo problem.
Notice how the teacher asks students to think about why the setup of their proportion works. He acknowledges it as good, which is encouraging to the students, but still wants them to think deeply about it.
He also gives ample wait time after asking groups questions, this allows them to think and puts the honus on the students. He is pushing them to think about why their procedures work and what things are (what does the 9 represent).
He also encourages them to try different methods. This can help the multiple methods for solving proportional reasoning problems to emerge from the students.
