This study is developmental research that aims to develop a Realistic Mathematics Education (RME) learning set to improve mathematical concepts understanding of 8th grade students in junior high school that has valid, practical, and effective qualifications. This study uses the ADDIE model. The instruments used in this study are a validation sheet to measure validity aspects, a student response questionnaire to measure practicality aspects, and a conceptual understanding test to measure effectiveness aspects. The result of this study is a Realistic Mathematics Education learning set in polyhedron subject to improve mathematical concepts understanding skills of 8th grade students in junior high school. In general, the developed learning set is of good quality. The validity aspect of the learning set meets a very good category with an average score of a lesson plan is 4,66 from the maximum score of 5 and the average score of a student worksheet is 4,44 from the maximum score of 5. The practicality aspect of the learning set meets a good category with an average score of students' response questionnaire is 4,04 from the maximum score of 5. And the effectiveness aspect of the learning set meets a good category based on the percentage of students' mastery learning at posttest which is 61%, and the increase in the average score of pretest to posttest, from 38,52 to 73,35.
Nailurrohmah et al. (Sat,) studied this question.