Abstract
The purpose of this research is to clarify a method of the class practice and its effects introducing the idea of the limit in the unit "Area of Circle". We considered that 61 6th grade students of two classes were the experimental group and 63 6th grade students of two classes were the controlled group. For the students of the experimental group, we carried out the class practice of the unit "Area of Circle" introducing the idea of the limit, in accordance with
arithemetic activities of investigations and searches. For the students of the controlled group, we
taught according to the contents of the textbook. In the posttest, Problem 1 was contents of equal partitions of the circle and sectors arranged by turns, and Problem 2 was advanced those of the textbook of T Co. As a result of analyzing and considering of the posttest, we clarified the following.
(1) For Problem 1, the percentage of correct answers of the experimental group was 90.2% and
that of the controlled group was 57.1%.
(2) For Problem 2, the percentage of correct answers of the experimental group was 93.4% and
that of the controlled group was 58.7%.
Judging from these results, we found that the class practice introducing the idea of the limit was easy to understand for students and it was effective.
