Exploring the challenges of teaching similarity of triangles, the case of Areka town primary schools, Ethiopia

Abstract

Similarity and its related concepts are central components of geometry. It is an important spatial-sense and geometrical concept that can facilitate students’ understanding of indirect measurement and proportional reasoning. Many see geometry as a significant subject in mathematics and the similarity of a triangle is found to be a key concept within geometry, but there is very little research done on teachers’ challenges on teaching similarity of triangles. Thus, this study focused on exploring the challenges of teaching similarity of triangles in Grade 8 classes and how those challenges could be minimised. A qualitative and exploratory case study design was used. In addition, purposive sampling was used to select 5 mathematics teachers from Areka Town primary schools, in Ethiopia. In this regard, the data of this study were collected using classroom observation, semistructured interview, and teachers’ questionnaire. The data were coded manually and categorised into four themes. Based on the data, the findings in this study indicated that teachers faced mathematical knowledge and pedagogical knowledge challenges. In relation to this fact, students’ poor background knowledge, resources, and the mathematics curriculum were also among the challenges teachers faced in teaching the similarity of triangles. The teacher-student interaction was minimal, and the teaching approach was dominated by teacher talk and chalk. Based on the literature reviewed, a theoretical framework that underpinned this study, and empirical data obtained, the researcher proposed a model for meaningful teaching on the similarity of triangles and used it to minimise the challenges of teaching the similarity of triangles. A meaningful teaching similarity of triangles refers to providing an activity that offers an opportunity for students to connect the similarity of triangles to their real-life experiences and has a goal to connect the similarity of triangles to real-life situations. Through the interventions using the prosed model, the participants were able to explain models of similar figures, polygons, and the application of the similarity of triangles in the real life. Furthermore, the teaching approaches used by the participants have come to show van Hieles’ five phases of instruction for teaching of similarity and in this regard, participants had known the van Hieles’ theories and its importance for meaningful teaching similarity of triangles. This study further recommends the reform of pre-service teachers’ education, incorporating continuous professional development, revising the geometric contents in the existing syllabus, and including the different theories related to teaching and learning geometry in the mathematics syllabus.