Investigation of high school students' proportional reasoning ability

The aim of this study is to examine the change of proportional reasoning skills of high school students in a teaching experiment approach. The study was carried out with four participants in 10th grade. The study was started by determining the proportional reasoning skill levels of the participants before the application, and then an individual teaching experiment was applied and finally the proportional reasoning skill levels of the participants after the applied teaching experiment were determined. According to the results of the research, proportional reasoning is a skill that can be developed. The teaching experiment, which consists of a series of sessions prepared according to a certain systematic order used in the research, was effective in developing participants' proportional reasoning skill levels. According to this teaching experiment, first of all, students should be able to link between the two quantities (measures) in order to improve the proportional reasoning levels of participants. After the two quantities can be noticed, students should be able to switch from the additive comparison to multiplicative comparison with composed-unit strategies to forming a ratio between two quantities. Then, participants should be transitioned from using only composed-unit strategies to making and using multiplicative comparisons as well. Finally, participants should be transitioned from developing a few easy equivalent ratios to creating a set of infinitely many equivalent ratios. In addition, in order to help participants develop their proportional reasoning skills, learning environments should be supported with materials that enable visualization.