Abstrak
This was a quasi-experimental research with a posttest only control design. The independent variable in this study was a realistic mathematics approach and the dependent variable is students’ understanding of mathematical concepts. The population in this study were all students of class VIII at SMP Negeri 12 Tarakan. Samples were taken using simple random sampling technique, namely 32 class VIII-4 students as the experimental group and 32 class VIII-5 students as the control group. Data collected by written test and documentation. Data were analyzed using descriptive analysis and inferential analysis (independent sample ttest) with the help of SPSS 23.0 software for windows. The average posttest score in the experimental class was greater than the average posttest value in the control class, 70.37 compared to 55.80. While the results of the independent sample t-test with a significant level of 5% ( = 0.05) obtained a p-value of 0,000. Thus was rejected and was accepted, so it could be concluded that the approach influenced students’ ability to understand mathematical concepts.