In this paper, I discuss the potential transformations to teach K-12 geometry topics with the technology of 3D Pens, which enabled 3D models to be created instantly via one's moving hands. I draw on an example of using constructionist learning activities with 3D Pens to teach young children, 'how tall is the triangle?'

The aim of this study is to determine pre-service classroom teachers' beliefs and thoughts about the roles of teachers and students in the classroom before taking the Mathematics Teaching I course. With this purpose, the study employed the survey method, a descriptive research technique. The study sample included 75 pre-service teachers (55…