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1、因数和倍数教学设计横街小学杨起凤教学内容:人教版五年级下册第5 页和第 6 页教学目标:(一)知识与技能理解因数和倍数的意义以及两者之间相互依存的关系,掌握找一个数的因数和倍数的方法,发现一个数的倍数、因数中最大的数、最小的数,及因数和倍数个数方面的特征。(二)过程与方法通过整数的乘除运算认识因数和倍数的意义,自主探索和总结出求一个数的因数和倍数的方法。(三)情感态度和价值观在探索的过程中体会数学知识之间的内在联系,在解决问题的过程中培养学生思维的有序性和条理性。教学重难点:教学重点:理解因数和倍数的含义。教学难点:自主探索有序地找一个数的因数和倍数的方法教学过程:(一)导入新课:由人与人之间
2、的相互依存关系,引出数与数之间的相互依存关系。(二)教学例 1:1观察算式的特点,进行分类。(1)仔细观察算式的特点,你能把这些算式分类吗?(2)交流学生的分类情况。(预设:学生会根据算式的计算结果分成两类)第一类是被除数、除数、商都是整数;第二类是被除数、除数都是整数,而商不是整数。2明确因数和倍数的意义。(1)同学们,在整数除法中,如果商是整数而没有余数,我们就说被除数是除数的倍数,除数是被除数的因数。例如,12 2=6,我们就说12 是 2 的倍数,2 是 12 的因数。12 6=2,我们就说12 是 6 的倍数,6 是 12 的因数。(2)在第一类算式中找一个算式,说一说,谁是谁的因数
3、?谁是谁的倍数?(3)强调一点:为了方便,在研究倍数与因数的时候,我们所说的数指的是自然数(一般不包括 0)。【设计意图】引导学生从“整数的除法算式”中认识因数和倍数的意义,简洁明了,同时为学习因数和倍数的依存关系进行有效铺垫。3理解因数和倍数的依存关系。我们能不能说“4是因数”“24是倍数”呢?表述时应该注意什么?【设计意图】引导学生在理解的基础上进行正确表述:因数和倍数是相互依存的,不是单独存在的。我们不能说4 是因数,24 是倍数,而应该说4 是 24 的因数,24 是 4 的倍数。(三)找一个数的因数教学例 2:1探究找18 的因数的方法。(1)18 的因数有哪些?你是怎么找的?(2)
4、交流方法。预设:方法一:根据因数和倍数的意义,通过除法算式找18 的因数。因为 18 1=18,所以 1 和 18 是 18 的因数。因为 18 2=9,所以 2 和 9 是 18 的因数。因为 18 3=6,所以 3 和 6 是 18 的因数。文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9
5、HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T
6、3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9
7、HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T
8、3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9
9、HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T
10、3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7方法二:根据寻找哪两个整数相乘的积是18,寻找 18 的因数。因为 1 18=18,所以 1 和 18 是 18
11、的因数。因为 2 9=18,所以 2 和 9 是 18 的因数。因为 3 6=18,所以 3 和 6 是 18 的因数。2明确 18 的因数的表示方法。(1)我们怎样来表示18 的因数有哪些呢?怎样表示简洁明了?(2)交流方法。预设:列举法,18 的因数有:1,2,3,6,9,18。集合图示法。3练习找一个数的因数。(1)你能找出30 的因数有哪些吗?36 的因数呢?(2)怎样找才能不遗漏、不重复地找出一个数的所有因数?【设计意图】让学生通过自主探索、交流,获得找一个数的因数的不同方法,在练习中体会“一对一对”有序地找一个数的因数,避免遗漏或重复。初步感受一个数的因数的个数是有限的,以及“最大
12、因数、最小因数”的特征。(三)找一个数的倍数教学例 3:1探究找2 的倍数的方法。(1)2 的倍数有哪些?你是怎么找的?(2)交流方法。预设:方法一:利用除法算式找2 的倍数。因为 2 2=1,所以 2 是 2 的倍数。因为 4 2=2,所以 4 是 2 的倍数。因为 6 2=3,所以 6 是 2 的倍数。文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3
13、I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:C
14、P7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3
15、I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:C
16、P7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3
17、I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:C
18、P7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7方法二:利用乘法算式找2 的倍数。因为 2 1=2,
19、所以 2 是 2 的倍数。因为 2 2=4,所以 4 是 2 的倍数。因为 2 3=6,所以 6 是 2 的倍数。(3)2 的倍数能写完吗?你能继续找吗?写不完怎么办?(4)根据前面的经验,试着表示出2 的倍数有哪些?(预设:列举法、图示法)2练习找一个数的倍数。你能找出 3 的倍数有哪些吗?5 的倍数呢?【设计意图】在理解“倍数”的基础上,让学生进一步体会有序思考的必要性。初步感受一个数的倍数的个数是无限的,以及“最小倍数”的特征。(四)一个数的因数与倍数的特征1从前面找因数和倍数的过程中,你有什么发现?2讨论交流。3归纳总结。预设:一个数的因数的个数是有限的,最小的因数是1,最大的因数是它
20、本身;一个数的倍数的个数是无限的,没有最大的倍数,最小的倍数是它本身。1 是所有非零自然数的因数。(五)巩固练习(六)板书设计因数和倍数相互依存不为 0 的自然数方法:有序思考文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8
21、L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2
22、Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8
23、L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2
24、Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8
25、L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7文档编码:CP7T2T8L3Q9 HF6I2L9H3I5 ZE2Y5O8T3X7
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