• School Mathematics
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• v.10 no.1
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• pp.123-138
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• 2008

The objective of this paper is to reveal the cause of failure of New Math in the field of the SMSG area education from the didactical point of view. At first, we analyzed Euclid's (Elements), De Morgan's (Elements of arithmetic), and Legendre's (Elements of geometry and trigonometry) in order to identify characteristics of the area conception in the SMSG. And by analyzing the controversy between Wittenberg(1963) and Moise(1963), we found that the elementariness and the mental object of the area concept are the key of the success of SMSG's approach. As a result, we conclude that SMSG's approach became separated from the mathematical contents of the similarity concept, the idea of same-area, incommensurability and so on. In this account, we disclosed that New Math gave rise to the lack of elementariness and geometrical mental object, which was the fundamental cause of failure of New Math.