Abstract

It is difficult for students to solve proportion problems. This case study describes how students solve proportion problems by taking heed of mental mechanisms, namely interiorization, coordination, encapsulation, and generalization. The subjects in this study were the seventh graders of junior high schools in Yogyakarta, Indonesia. The subjects were chosen purposively, namely paying attention to subjects’ mistakes in solving proportion problems. The findings show that students undergo problems in the division, and they are unable to formulate the right formula even though they know the concept of proportions, mixed solutions to direct proportion and inverse proportion