This paper focuses on Michael, one of four seventh grade students who participated in a study involving a constructivist teaching experiment. In the study, manipulatives within a computer microworld were used to solve fractional reasoning tasks and tasks that involved concepts of rate, ratio, and proportionality. Pretest results are presented, and instruction on fractional reasoning and word problems is described. It is concluded that Michael left the experiment possessing more sophisticated fractional reasoning operations available to him than when he entered the experiment. (Contains 17 references.) (MES)