Learning goals: Teacher Facing Calculate the constant of proportionality for a proportional relationship in an unfamiliar context, and express it (in writing) using the correct units. Critique (orally and in writing) presentations of proportional and nonproportional relationships. Invent and describe (in writing and using other representations) a proportional relationship and a nonproportional relationship. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 7.2 Introducing Proportional Relationships, Grade 7.