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Why is a spaghetti bridge full of triangles?

7th GradeTrianglesabout 3 minCCSS 7.G.A.2

Push a square and a triangle made of pinned sticks, then brace your own bridge.

Lesson Plan

Explore when three side lengths determine a unique triangle.

  1. Big idea: Pause. Ask a student to say the idea in their own words.

  2. Question: Ask what students spot and what they are curious about. Read “Can the square change its shape?” aloud. Have each student guess and say why.

  3. Question: Read “Which fix stops the leaning?” aloud. Have partners explain their guesses to each other.

  4. Big idea: Pause. Have partners explain the idea to each other.

  5. Big idea: Pause. Ask how this idea connects to the last one.

  6. Your turn: Have students try their own. Ask them to predict before they test.

How to run it

  1. Whole classPut the lesson on the board. At each choice the class votes, then you select the winner.
  2. SoloShare the link, QR code, or post to Google Classroom. Each student gets to take their own path.