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 1, 2:54
To help the students determine whether or not the situation is proportional, the teacher has them create a table for the data. She is establishing this method as a way of determining whether or not a scenario is proportional for her classroom.
Notice that she has them recall the definition of proportionality. This can help her as an instructor know what the students' conceptions of proportionality may be and give her insight in to where they need help. Ask this question as necessary.
In addition to having the definition come out through discussion, she demonstrates how the definition can be used to determine whether or not something is proportional.
She also demonstrates how the ratio is not proportional. To know what something is, it is also helpful to know what it is not.
