A design experiment with 18 students in a regular seventh grade math class was conducted to investigate how to differentiate instruction for students' diverse ways of thinking during a 26-day unit on proportional reasoning. The class included students operating with three different multiplicative concepts that have been found to influence rational number knowledge and algebraic reasoning. The researchers and classroom teacher tiered instruction during a 5-day segment of the unit in which students worked on problems involving speed. Students were grouped relatively homogenously by multiplicative concept and experienced different number choices. Students operating at each multiplicative concept demonstrated evidence of learning, but all did not learn the same thing. We view this study as a step in supporting equitable approaches to students' diverse ways of thinking, an aspect of classroom diversity. [For the complete proceedings, see ED606556.]