In this clip the teacher asks the students to come up with their own definition of what it means for two quantities to be proportional.
Definition of Proportionality, Clip 2, 6:08
It is important to constantly have the students attending to the definition of proportionality. This is an example of a discussion that can take place when trying to get students to verbalize what they think proportionality is.
Notice that the teacher is constantly requiring that students give justifications for their answers. It is important to encourage this type of behavior from the students.
She also negotiates the tables to be tools students can use to determine whether or not data is proportional.
