The mathematical reasoning ability of junior high school students remains a major issue in mathematics learning. Many students still focus on the final answer and memorize formulas without understanding the underlying thought processes. This condition indicates that students’ abilities to provide logical reasons, draw conclusions, and make generalizations are still relatively low. This study aims to analyze the mathematical reasoning ability of junior high school students in solving problems related to quadrilateral shapes. The research employed a qualitative descriptive method with subjects consisting of eighth-grade students from UPT SMP Negeri 1 Rembon, selected based on high, medium, and low academic ability levels. The research instruments included a mathematical reasoning test and interview guidelines for three main subjects. The data obtained were analyzed through the stages of data reduction, data presentation, and conclusion drawing. The results revealed that students’ mathematical reasoning abilities were generally low. Most students were unable to make appropriate conjectures, perform correct mathematical manipulations, or provide logical justifications. Furthermore, students also faced difficulties in drawing conclusions from relationships between concepts in plane geometry.
Ira Lavenia1*, Lusiana Delastri2, Inelsi Palengka3, Suri Toding Lembang4 (2026) studied this question.