We started our geometry unit with an introduction to polygons. Polygons are flat (2-D), closed figures with three or more straight sides that don’t cross. We sorted polygons on the Activboard.
Then we read the The Greedy Triangle by Marilyn Burns. Bored and dissatisfied with his life, a triangle visits a local shapeshifter to add another side and angle to his shape. Poof! He becomes a quadrilateral. But then he gets greedy and keeps adding angles until he’s completely transformed. As we read the story, the children used Popsicle sticks to make each polygon.