To detect the differences among various instructional materials and methods in the effectiveness in attaining the goal, two programmes were compared. Seventh and fifth graders were divided into matching pairs in terms of test scores and school records, and then one of each pair was assigned to program A and another to program B. Program A did not use the number line, while program B used it. No difference in passing ratio was found between two groups. Comparison in terms of percentrge of correct answer did not reveal significant difference either.