IMPLEMENTATION OF GROUP INVESTIGATION LEARNING MODEL TO IMPROVE PROBLEM SOLVING ABILITY IN CLASS VIII IN SMP NEGERI 11 MEDAN ACADEMIC YEAR 2014/2015

The purpose of this study was to: 1) To know the big of the improvement of students` problem solving ability using Group Investigation learning model on the matter cubes and beams in SMP Negeri 11 Medan in Academic Year 2014/2015.2) To know the process of students` answer in improving the problem solving ability in topic cubes and beams in SMP Negeri 11 Medan Academic Year 2014/2015. Type of this research is the Classroom Action Research (CAR), which was implemented in SMP Negeri 11 Medan.The subjects were students of class VIII-7 school year 2014/2015, consist of 48 people consisting of 20 boys and 28 girls. The object of this research is the ability of mathematical problem solving, the process of students` answer, student activities and model of group Investigation (GI). This study consisted of two cycles, the first cycle consists of two meetings and the second cycle consists of two meetings. The results of this study could be seen: (1) The process of implementation problem based learning was running well because the observation of implementation based teacher side is good category and student side is active category. (2) The improvement of problem solving ability of students by the implementation of group investigation learning model belongs to high category with the normalized gain value is 0.83 where the average of problem solving ability of students in cycle I is 48.16 and in cycle II the average is improved become 91.02. (3) The process of students` answer is improve from the cycle 1 to cycle II. There are 80% of students to meet the minimum completeness criteria after learning activities using group investigation learning model in small study groups. It is seen from the percentage of the first cycle is 41% of students that get category good enough or more while the percentage of the second test result is 92% that get category good enough or more. From the results of this study concluded that the implementation of Group Investigation learning model can improve students` problem solving.