REKA BALQIS Pengarang As Elly S, M. Pd. Mat. Dosen Pembimbing 1 Dr. Khathibul Umam Zaid Nugroho, M.Pd. Dosen Pembimbing 2 As Elly S, M. Pd. Mat. Ketua Penguji Lucy Asri Purwasi, M.Pd.Mat. Penguji 2 Nur Fitriyana, M. Pd. Mat. Penguji 1 REKA BALQIS Contributor

This study aims to determine the ability to understand students' concepts in circle material after being given learning using the Problem based learning model. This study is a quasi-experiment research using the One-Group Pretest-Posttest Design. The population of this study is all students of class VIII of MTS Ittihadiyah Karang Dapo. Data collection techniques are carried out through tests and observations. The data analysis techniques used in this study were normality test and hypothesis test. The results of the study showed that the average pre-test score was 56.52 and the post-test score was 78.42. The t-test shows that the result of ,t-calculate. = 2,379 and obtained ,t-table. = 9,488 so that it is obtained that ,t-calculate. 6,869> ,t-table. 9.488, this means that H-a. is accepted and H-0. is rejected. Thus, the hypothesis proposed in this study can be accepted, so it can be concluded that the ability to understand the concept of grade VIII students of MTS Ittihadiyah Karang Dapo after being given learning using the problem-based learning model in mathematics learning in the Circle material is in the good category. Keywords: Problem Based Learning Model, Circle, Concept Understanding Ability