With the Constructive Triangles, the child explores how triangles relate to and can be the building blocks of other plane figures. The 1st Rectangular Box relates various types of triangles to various types of quadrilaterals, from squares to rhombi. This material provides practice at visualizing and manipulating straight-sided figures in new ways, ones that will be applicable when the child studies equivalence and area in Elementary.

This material includes:

- 1 box
- Assorted triangle shapes