Learning goals: Teacher Facing Create and describe (in writing) graphs that show measurements of squares. Justify (orally and in writing) whether the relationship shown on a graph is close enough to a straight line through the origin that it might be a proportional relationship with some measurement error. Recognize that when we measure the quantities in a proportional relationship, measurement error can cause the graph to be not perfectly straight and the quotients to be not exactly constant. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 7.3 Measuring Circles, Grade 7.