This study addressed the problem of how a prospective mathematics teacher's active engagement in a scientific inquiry can deepen the meaning of her extant mathematical concepts. We used a constructivist framework to analyze a 2-hour interview with a prospective mathematics teacher as she solved an open-ended problem of graphing a 3-D landform. We found two overlapping components in her learning via cycles of action and reflection: interpreting the task and reorganizing extant conceptions to quantify projective, horizontal/vertical distances. [For complete proceedings, see ED489597.]