National Security Agency
Classifying Triangles
Building on young mathematicians' prior knowledge of three-sided shapes, this lesson series explores the defining characteristics of different types of triangles. Starting with a shared reading of the children's book The Greedy Triangle,...
PBS
Accessible Shapes
All the 2-D and 3-D measurement work you need is in one location. Divided into three sections, the geometry lesson plans consist of visualization of three dimensions, classifying geometric figures, and finding surface area and volume....
Shodor Education Foundation
An Introduction To Quadrilaterals
Young geometers investigate and apply properties of quadrilaterals. After a review and discussion of key terms, students use a computer applet to explore four-sided figures and classify them according to their attributes. The...