The number of collections and the capabilities of virtual manipulatives (VMs) has grown considerably during the past twenty-plus years. A VM is “an interactive Web-based visual representation of a dynamic object that presents opportunities for constructing mathematical knowledge” (Moyer, Bolyard, and Spikell 2002). VMs come in a variety of platforms (e.g., java, html5, flash, cdf, etc.) and as apps for tablets (e.g., iPad and Android). Additionally, I consider preconstructed dynamic geometry objects (e.g., dynamic worksheets constructed and published using GeoGebra) as VMs due to the interactive nature of these dynamic objects.
Lindsay Reiten, lindsay.reiten@unco.edu, is a mathematics teacher educator at the University of Northern Colorado in Greeley. A former middle and high school mathematics teacher and university lecturer, she is interested in teacher education and supporting teachers' modification and integration of technology-based activities.