The purpose of this study is to investigate students' thinking of direct, inverse and nonproportional problems. Thirty two seventh grade students from three different government schools participated in this study. To collect the data, the participants were asked to solve 9 open-ended problems, including 3 direct, 3 inverse and 3 non-proportional…

This study introduces an effective intuitive rule focusing on "tending to the midpoint" in individuals' mathematical thinking. The rule concerns the intuitive tendency towards choosing the midpoint of a change, as a salient point among all the points. To test the proposed rule, 120 students in grade 9 were interviewed. We analyzed the…