Reflection: Student Ownership Going Deeper with Interior and Exterior Angles - Section 3: Think-Group-Share: Three Polygons Meet at Point B


This is the kind of problem that I love to showcase in a whole-class discussion as it provokes interest by posing a question students actually want to answer—this is important.  Equally important is the fact that this problem can be solved in multiple interesting ways, which reinforces the message that the answer is not nearly as valuable as the thinking and problem solving efforts that lead students to be able to arrive at the same, logical conclusion.

As students first shared out initial thoughts and ideas in their small groups, I circulated the room, listening carefully to understand and differentiate between students’ solution paths.  I chose student presenters in an order that I thought would promote the deepest understanding of the problem amongst the greatest number of students. I essentially looked for a student who would start the discussion by sharing a widely used and fairly traditional approach (by using the interior angle measure of the unknown polygon and the interior angle sum formula) to start the share-out discussion; this also meant that I looked for different and perhaps novel approaches (sketching an exterior angle to the unknown polygon and visualizing the number of times that exterior angle would fit into 360 degrees, for example).  The order, I think, matters in that it allows the greatest number of students the most access and opportunity to deeply understand important relationships.

  Using a Simple Yet Engaging Problem to Publicly Value Multiple Approaches
  Student Ownership: Using a Simple Yet Engaging Problem to Publicly Value Multiple Approaches
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Going Deeper with Interior and Exterior Angles

Unit 8: Discovering and Proving Polygon Properties
Lesson 3 of 9

Objective: SWBAT justify their reasoning when solving a diagram for missing angle measures.

Big Idea: By working on a Hands-On Activity in groups students develop collaboration skills and practice justifying their conjectures.

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Math, Geometry, polygons (Determining Measurements), problem solving, properties of polygons, angles and angle measurement
  55 minutes
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