IMPLEMENTATION OF NUMBERED HEAD TOGETHER MODEL TO IMPROVE THE STUDENTS UNDERSTANDING OF MATHEMATICAL CONCEPT IN THE LINEAR EQUATION SYSTEM OF TWO VARIABLES CLASS VIII AT ACADEMIC YEAR 2013/2014

This research starts from low degree of students understanding of mathematical concept with the root of problem is irrelevance learning model which usually implemented by teacher. This research aimed to (1) knowing how is the degree of students conceptual understanding in linear equation of two variables system after Numbered Head Together model has been implemented, (2) describing the level of students activity in implementation of Numbered HeadTogether model. This research is class action research. The subject of this reseacrh is students in class VIII-5 SMP Negeri 5 Percut Sei Tuan with total students is 28 students. The object of this research is the conceptual understanding of students and also the students activity in linear equation of two variables system by implementing the cooperative learning strategy of Numbered Head Together model. The average score of prerequisite test based on data analysis is 67.25. The results of data analysis in cycle I are: (1) the average score of students conceptualunderstanding test in cycle I is 58, (2) student in very low category is 2 students (7%), (3) student in low category is 8 students (29%), (4) student in middle category is 12 students (43%), (5) student in high category is 6 students (21%), (6)and there is no student in very high category, (7) the used time for independent learning is 86.1% of available time and 13.2% of available time spent to interact with the teacher. The result of data analysis in cycle II is (1) the average score of conceptual understanding test is 72.57, (2) there is no student in very low and lowcategory, (3) there are 11 students (39%) with middle prosperity, (4) there are 14 students (50%) in high category, (5) there are 3 students (11%) in very high category, (6) about 88.05% of available time, used by student to learnindependently, and about 12.02% of available time used by students interact with a teacher. From the result of research concluded that implementation of Numbered Head Together model able to improve the students understanding ofmathematical concept, and learning process are conducted well observed bystudents learning activity. Based on this conclusion, it is expected that this research can be used as reference to improve the students conceptualunderstanding.