2010 年 16 巻 1 号 p. 1-14
In this paper I consider an arithmetic in "Das Zahlanbuch 1" and bring out the following points. (1) In "Das Zahlenbuch 1" the authors are conscious of a dynamic structure of operation. And it has a substructure. Ex. from simple formulas to complex formulas. (2) They make much of "power of five". Since objects under five are optically grasped simultaneously, children must not count objects. (3) Children understand knowledges under rich relationships. (4) We have to understand mathematics as a "science of patterns". (5) Authentic situations are more important than earlier. (6) From a point of methodology, openness of teaching is guaranteed both the property of subject and the development of children. (7) Structure-oriented and application-oriented teachings are achieved harmonically.