Learning goals: Teacher Facing Use the word “reciprocal” to explain (orally and in writing) that there are two related constants of proportionality for a proportional relationship. Write two equations that represent the same proportional relationship, i.e., $y=kx$ and $x=(\frac{1}{k})y$, and explain (orally) what each equation means. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 7.2 Introducing Proportional Relationships, Grade 7.