Mathematical Practices of Eighth Graders about 3D Shapes in an Argumentation, Technology, and Design-Based Classroom Environment

This design research investigated the mathematical practices that eight graders (14-year-old students) developed when learning about prisms, cylinders, and their surface areas. An inquiry-based learning environment was created for students to engage in argumentation. The instruction was enriched by use of a dynamic geometry software, namely GeoGebra, to assist students in visualizing and reasoning about 3D shapes. Rasmussen and Stephan’s three-phase method (2008) was used to organize the collected data, which in turn were analyzed using Krummheuer’s model of argumentation (2015). The results indicated the emergence of three mathematical practices and several taken-as-shared ideas: (1) defining prisms, (2) computing the surface area of a prism, and (3) computing the surface area of a cylinder. The study’s results revealed that students’ understanding improved when learning concepts simultaneously with argumentation and dynamic geometry software.