THE IMPLEMENTATION OF COOPERATIVE LEARNING MODEL NHT TYPE TO IMPROVE STUDENT`S PROBLEM-SOLVING IN GRADE XII AT SMA SWASTA YPI DHARMA BUDI

The aim of this research is to improve students’ mathematics problem solving ability in the classroom taught using cooperative learning mode type Numbered Head Together (NHT). The design of this research is Classroom Action Research (CAR). The object of this research is the implementation of NHT model. The subject of this research is all students in grade XII Mia 2 SMA Swasta YPI Dharma Budi Academic year 2019/2020 consist of 36 students. The result of this research are: (1) The number of students who reach category completed for Mathematical Problem Solving Ability test in cycle I are 14 persons with percentage of completeness is 38,89%, students not completed are 22 persons with percentage of completeness is 61,11% and the score of problem solving ability reached is 2,58 in the low criteria.(2) The number of students who reach category completed for Mathematical Problem Solving Ability test in cycle II are 32 persons with percentages of completeness is 88,89%, students not completed are 4 persons with percentages of completeness is 11,11% and the score of mathematical problem solving ability reached is 3,25 in high category, (3) percentage of classical in the process of solving students' answers in every aspect of problem solving ability. The aspect of understanding the problem of the first cycle is 97.22% increasing in the second cycle to 100%. The planning aspect of the first cycle was 41.67%, increasing in the second cycle to 77.78%. The implementation aspect of the first cycle was 66.67%, increasing in the second cycle to 91.67%. The aspect of checking back from the first cycle is 69.44%, increasing in the second cycle to 72.22%, (4) learning by implemented cooperative learning model type NHT could make the students’ activity was good category in learning, (5) Learning by implemented cooperative learning model type NHT can improve students’ mathematics problem solving ability.