Is the natural number 7 rational? Is it complex? We argue that the answers to these questions relate to the ways numbers are taught. Commonly, a new kind of numbers is presented as an expansion of a previously familiar kind of numbers, which results in a nested image of the relations between number sets. In this article, we introduce an…

In this article we investigate how preservice elementary school (K-7) teachers understand the concept of prime numbers. We describe participants' understanding of primes and attempt to detect factors that influence their understanding. Representation of number properties serves as a lens for the analysis of participants' responses. We suggest that…

In our investigation of preservice secondary teachers' understanding of irrational numbers we focus on how different representations influence participants' responses with respect to irrationality. As a theoretical perspective we use the distinction between transparent and opaque representations, that is, representations that "show"…