We examine a prospective high school teacher's instructional representations of rate of change and right triangle trigonometry to investigate his interpretation and understanding in relation to the development of proportional reasoning. Despite a constant effort by the subject to resort to "real life" examples in order to give meaning to his teaching, as well as a fairly good understanding of how to connect the topic of instruction with the use of proportional reasoning, it occurs to us that the map of his conceptual moves is from ratio, to comparisons, to fractions. Once he enters the abstract world of fractional expressions and quotients, he often displays difficulties in re-connecting his ideas back to ratio. [For complete proceedings, see ED489597.]