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情報番号 1412 ヘルプ

タイトル: New says of Calculation
副題: 3rd grade Mathematics Lesson by Yasuhiro Hosomizu
著者: Masami Isoda
所属: Center for Research on International Cooperation in Educational Development (CRICED), University of
データ存在URL:

http://www.criced.tsukuba.ac.jp/math/video/02_New_Ways_of_Calculation.wmx

所在情報:

Streaming Searver, Center for Research on International Cooperation (CRICED), University of Tsukuba, Japan

データファイル:
対象国:
データの言語: 英語
キーワード: Lesson Study Calculation Expand
要旨:

The topic of this third grade lesson is around the calculation of a series of multiplications of two numbers between 20 and 30, in which their unit digits add up to 10 (e.g. 25x25; 24x26; 23x27; etc.). On the basis of such calculations, the goal of the lesson is to engage students in noticing patterns, finding an easier algorithm to perform the calculations, formulating a rule for such algorithm and explaining why it works. The new rule the students are supposed to find is: the result of such multiplications will be 600 plus the result of the multiplication of the two unit digits (e.g. 24 x 26 = 600 + 24). The rule can be easily formulated and justified in symbolic terms as follows:

(20+a)(20+(10-a))=600+a(10-a)

Obviously, third grade students lack these tools. Therefore, in order to produce and/or understand an explanation, they will have to resort to numerical methods. The teacher, in his subsequent debriefing with colleagues (as part of the open forum of the Lesson Study), says that he is aware that third graders also lack the tools fourth graders have, such as the area model.

Therefore the teacher plans to discuss the explanation, in a subsequent lesson, by building with the students a discrete version of the area model, using beads.

by Abraham Arcavi. (2007). New Ways of Calculation, Masami Isoda edited. Japanese Lesson Study in Mathematics. Singapore: World Scientific Publishing Co. 240-243

著者のHP: http://math-info.criced.tsukuba.ac.jp/  
作成出版日時: 2005/
関連プロジェクト:
情報登録課題名: 算数・数学教育
初期登録日時: 2007/06/10 10:17
最終更新日時: 2007/06/10 10:17
アクセス数: 1832(登録以来),  128(過去12ヶ月),  63(過去6ヶ月)
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