In this qualitative study, we investigated teachers' use of proportional knowledge resources while being asked to appropriately identify if a given situation was proportional or not using clinical interview data from a large grant funded project. We found that knowledge resources related to the mathematical structure of the situation were most…

Teacher knowledge, especially of proportional reasoning, is important, particularly in middle school grades in the United States. In this instrumental case study, one teacher's understanding of constant as it relates to proportions and how that understanding shifted over the course of a six hour professional development experience is discussed.…