小数の乗法における意味の拡張に関する実践的研究

抄録

The purpose of this paper is to suggest that the teaching focused on the extension of multiplication of decimal fractions at the fifth grade is effective to promote learner's understanding of its meaning. In the teaching of multiplication of decimals, we adopted the following three activities in the lesson. (1) Teaching of a number line before learning about the multiplication of decimals. (2) promote the expansion of teaching the meaning of multiplication of decimal. (3) Using a combination of number lines the multiplication of decimals and the study of percentages to promote learner's awareness of the mathematical structure on multiplication of decimals. Through the implementation of these experimental designs into the lessons of the multiplication of decimals at the fifth grade, the performance of many children was improved. The result of the post-test showed that the students were able to understand the meaning of multiplication of decimals. But, there were some difficulties for each learner to realize the extension of its meaning. We need to improve the lesson designs according to a learner's situation of understanding. Especially, the standardization of the lesson of multiplication of decimals and the way of using the number line are two major tasks for now.