[教学内容]人教版五年级下册第二单元《3的倍数的特征》。[教材分析]本节教学内容是学生在学习了2和5的倍数特征之后学习的新知识,它又是学习质数与合数、分解质因数等新知的基础。从主题图中可以看出,编者意图是让学生在定势思维失败的情况下另辟蹊径,变向思维探究。从简单3的倍数入手, [Teaching content] PEP fifth grade second volume second unit “3 multiple characteristics.” [Textbook Analysis] The content of this lesson is a new knowledge that students learn after learning the multiplicative features of 2 and 5. It is also the basis for learning new knowledge such as primes and co-ordants, and factoring in the quality. As can be seen from the theme map, the editor's intent is to let students find another way in the case of the failure of fixed-thinking thinking, change to thinking to explore. Starting from the simple multiples of 3,