The purpose of this activity is for students to identify the attributes that make a quadrilateral a rectangle, a rhombus, or a square. Students study examples and non-examples, looking for features that each set has in common and draw conclusions accordingly (MP7). The goal is not to craft the most precise definition for each, but to develop an understanding of the defining geometric attributes.

• Invite 1–2 groups who analyzed rectangles to share their responses. Record their responses.
• Ask the class:
  • “Do you agree with the shapes that are marked as rectangles (or rhombuses or squares)?”
  • “Do you agree with the descriptions?”
  • “Is there any part of the descriptions you’d say differently?”
  • “Is there anything you'd add to the description?”
• When students have finished describing rectangles, highlight that: “A shape is a rectangle if it is a quadrilateral with 4 right angles.”
• Repeat the discussion with rhombuses and squares. Highlight that:
  • “A shape is a rhombus if it is a quadrilateral with equal sides."
  • "A shape is a square if it is a quadrilateral with equal sides and 4 right angles."