Learning goals: Teacher Facing Calculate the weight of an unknown object using a hanger diagram, and explain (orally) the solution method. Comprehend that adding and removing equal items from each side of a hanger diagram or multiplying and dividing items on each side of the hanger by the same amount are moves that keep the hanger balanced. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 8.4 Linear Equations and Linear Systems, Grade 8.