This article provides detailed analysis, from a radical constructivist perspective, of a sequence of letter-writing exchanges between a preservice secondary mathematics teacher and a high school student. This analysis shows the ways in which the preservice teacher gained understanding of the high school student’s mathematics and attempted to pose tasks accordingly, leading to a fruitful mathematical exchange. In addition, this article also considers the same exchange from what could be considered broadly as a situated perspective towards learning. We conclude by suggesting that these perspectives could be considered compatible within this study if a distinction is made between the student’s point of view and the researcher’s.