This research was aimed to reveal: 1) the difference between studying mathematics by the use of a contextual teaching – learning approach with VCD and the one with LKS as the media towards mathematics learning competency, 2) the difference among students of high, of moderate, and of low interests in learning mathematics towards mathematics learning competency, 3) the interaction between the use of media assisted learning approach and students’ learning interest towards mathematics learning competency a media studying approach and interest of students to study towards reaching a mathematics studying competency.

This research belongs to a quasi experiment. It was conducted in March up to May 2008. The population of the research was the eighth year students of State Junior High School of Karanganyar. The data were collected by the use of documentation, questionnaire, and test techniques. In order to determine whether all points of the questionnaire measured the same thing and showed the same tendencies, Internal Consistency Test was applied together with Product – Moment Correlation of Karl – Pearson. Analysis prerequisite made use of Lilliefors test to examine the normality and Bartlett test to examine the homogeneity.

The data analysis technique used was Two Way Variance Analysis with different number of cells. The result of Two Way Variance Analysis for the 5% standard showed: (1) there were differencies in effectiveness between the contextual learning approach using VCD and the one using LKS as the media towards students’ mathematics learning competency, (2) the high, middle, and low levels of students’ learning interest gave different effects to the students’ mathematics learning competency, and (3) there was no difference between media assisted learning approach and the levels of students’ learning interest towards students’ mathematics learning competency.