This is a supplemental activity to any Common Core Curriculum that teaches Mathematical Practice 3: Construct Viable Arguments and Critique the Reasoning of Others. This activity can be taught in small groups or whole group. First, the students read the problem (purposely solved incorrectly). The students have to "construct a viable argument", as stated in the standard, to prove or disprove the problem. They have to justify their answers in writing and in a picture, identify the mistake and solv