Teaching geometry courses for preservice elementary teachers, we observed that difficulty with classifying shapes (and, in particular, composite 3-D shapes) persists even after work with simple shapes to support the writing of accurate and unambiguous definitions. We conducted a self-study of our teaching of 3-D concepts to uncover the concept…

Flexagons, introduced to a wide audience 50 years ago by Martin Gardner, now have an extensive literature and are an active field of research. This paper describes two kinds: edge flexagons and point flexagons, and gives an example of one means of classification.

Geometry, classification, and the classification of geometrical objects are integral aspects of recent curriculum documents in mathematics education. Such curriculum documents, however, leave open how the "work" of classifying objects according to geometrical properties can be accomplished given that the knowledge of these properties is the…

The activity of making a set of Logic Blocks is used to lead to a discussion of families of polygons and to questions about tessellations. (DT)

Multi-shaped blocks can be used to help young children develop many mathematical concepts and abilities. Several suggestions for using these blocks to create problem situations through which children develop concepts are offered. (SD)

Described are many concrete readiness activities within ten broad categories that are designed to provide children with a solid foundation for mathematics and that help prevent learning difficulties in mathematics. Preschool mathematical experiences form the foundation for all studies in mathematics. Without a sufficient number of appropriate…