April 2020's GPS department provides tasks for each grade band that invite students to reason with age-appropriate number theoretic concepts.
Kelly Hagan and Cheng-Yao Lin
Erin E. Baldinger, Matthew P. Campbell, and Foster Graif
Students need opportunities to construct definitions in mathematics. We describe a sorting activity that can help students construct and refine definitions through discussion and argumentation. We include examples from our own work of planning and implementing this sorting activity to support constructing a definition of linear function.