Some of these preservice instructors will be teaching in the context of theCommon Core State Standards for Mathematics (CCSSM), which emphasizes reasoning about ratios using “tables of equivalent ratios, tape diagrams, double number line diagrams, or equations” (CCSSI 2010, p. 42). With this in mind, we presented proportional reasoning as both a crosscutting theme across the three approaches and a topic that students often struggle with (Lamon 1999).