Teachers still often do problem judgments only on the end result, which is the main goal in learning and rarely pay attention to the process of solving the problem to the end result. Though the process of solving a problem to the end result is one of the interactive mindset (reasoning) between students and mathematics. This is one of the causes of low students' mathematical reasoning abilities. One approach to learning that is able to overcome the problem of low students' mathematical reasoning abilities is a problem-based learning approach. The purpose of this study was to determine that there is an increase in the students' mathematical reasoning ability of SMP Negeri 1 Syamtalira Aron taught through problem-based learning compared with conventional learning. This research was conducted by taking class samples at SMP Negeri 1 Syamtalira Aron school class VIII4 as experimental class and class VIII3 as control class by random sampling class, the method used is experimental method with control class design and experiment class and sample amounted to 51 students consisting of 27 for the experimental class and 29 for the control class. Research instrument using mathematical reasoning test. The statistical test used in this study is descriptive statistics to present inferential data and statistics of Student's test (t test). Before the first t test, homogeneity and normality tests were used with a significance level of 5%, and homogeneity test results showed F count <Ftable (1.11 <1.87) which means that both classes have homogeneous data. Furthermore, in the normality test for post test results showed that the experimental class Lo <Ltabel (0.1078 <0.187), which means normal experiment class data, and for the control class Lo <Ltabel (0.1034 <0.187) which means the control class data as well normally distributed. Based on the results of the analysis (t test) obtained the results of research that the significant value obtained from the t test that is titung 2.01> ttable of 1.67 at dk = 54 with 5% significant level. So it can be concluded that there is an increase in the students' mathematical reasoning ability SMP Negeri 1 Syamtalira Aron taught through problem-based learning compared with conventional learning.
