The aim of this study is to examine the process of forming the knowledge of the field of triangle. The process of forming knowledge and the interaction of two 6th grade students whose mathematics achievement is close to each other is discussed. Case study was chosen as the research method. In the case study, activity was designed as a data gathering tool and observation and interview were used to reveal the students' intellectual processes during the activity. The data analysis in the study was carried out with qualitative data content analysis. The process of generating information is examined on the basis of RBC+C abstraction theory. We can say that the instructional activities prepared from the data obtained contribute to the formation of the desired information.
Area of Triangle, Knowledge Formation, Abstraction, RBC+C.