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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,北师,大版,数学 五年级 上册,练习四（,2,）,复习旧知,课堂小结,课后作业,倍数,与,因,数,巩固练习,3,第1页,复习旧知,17,请将这些数按要求分类。,1,15,29,34,58,79,93,奇数,偶数,质数,合数,17,1,15,29,79,93,34,58,17,29,79,15,58,34,93,第2页,巩固练习,1.,读,一读，做一做。,第3页,阅读了以上材料，请你在下面括号里填上适当质数。,任何大于,4,偶数都能够写成两个质数相加形式。,10,（）（）,16,（）（）,40,（）（）,11,（）（）（）,15,（）（）（）,21,（）（）（）,3,7,7,9,17,23,任何大于,7,奇数都能够写成三个质数和。,3,3,5,2,2,7,3,5,7,5,5,5,2,2,11,7,7,7,3,5,13,5,5,5,11,5,5,3,13,5,11,11,29,3,37,第4页,2.,探,索活动。寻找质数。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,（,1,）,1,100,中哪些数是,质数,？一位聪明数,学家,想出了个寻找质,数,简单方法，在右,面,百数表中：,划掉,1,；,划掉除,2,外全部,2,倍数；,划掉除,3,外全部,3,倍数；,划掉除,5,外全部,5,倍数。,如,此做下去，剩下就是质数。,第5页,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,（,1,）,1,100,中哪些数是,质数,？一位聪明数,学家,想出了个寻找质,数,简单方法，在右,面,百数表中：,划掉,1,；,划掉除,2,外全部,2,倍数；,划掉除,3,外全部,3,倍数；,划掉除,5,外全部,5,倍数。,如此做下去，剩下就是质数。,第6页,（,1,）,1,100,中哪些数是,质数,？一位聪明数,学家,想出了个寻找质,数,简单方法，在右,面,百数表中：,划掉,1,；,划掉除,2,外全部,2,倍数；,划掉除,3,外全部,3,倍数；,划掉除,5,外全部,5,倍数。,如此做下去，剩下就是质数。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,第7页,（,1,）,1,100,中哪些数是,质数,？一位聪明数,学家,想出了个寻找质,数,简单方法，在右,面,百数表中：,划掉,1,；,划掉除,2,外全部,2,倍数；,划掉除,3,外全部,3,倍数；,划掉除,5,外全部,5,倍数。,如此做下去，剩下就是质数。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,第8页,（,1,）,1,100,中哪些数是,质数,？一位聪明数,学家,想出了个寻找质,数,简单方法，在右,面,百数表中：,划掉,1,；,划掉除,2,外全部,2,倍数；,划掉除,3,外全部,3,倍数；,划掉除,5,外全部,5,倍数。,如此做下去，剩下就是质数,。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,第9页,100,以内质,数,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,第10页,（,2,）在下表中圈出全部质数，并回答以下问题。,除了,2,，,3,两个质数外，其余质数都在哪几列？,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,除了,2,，,3,外，其余质数都在第一列和第五列。,第11页,（,2,）在下表中圈出全部质数，并回答以下问题。,把这个表扩大到,90,，圈出全部质数。它们都在,哪几,列,？,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,扩大到,90,，其余质数也都在第一列和第五列。,扩大到,100,以外，其余质数还是在第一列和第五列吗请同学们验证一下。,第12页,（,2,）在下表中圈出全部质数，并回答以下问题。,笑笑发觉了一个有趣结论：最小两个质数,相乘,得到,6,（,2,3,6,），用,6,去除其它质数，余,数一,定是,1,或,5,。这个结论对吗？试一试。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,从左表中看，这个结论是对。但还需要同学们继续验证哦。,“某个数除以,6,余数是,1,或,5,，这个数一定是质数。”,这种说法对吗？,6,倍数,6,倍数多,1,6,倍数多,5,第13页,第14页,这节课你们都学会了哪些知识？,100,以内质数：,课堂小结,2,，,3,，,5,，,7,，,11,，,13,，,17,，,19,，,23,，,29,，,31,，,37,，,41,，,43,，,47,，,53,，,59,，,61,，,67,，,71,，,73,，,79,，,83,，,89,，,97,。,第15页,这节课你们都学会了哪些知识？,课堂小结,这种筛选方法叫,埃拉托斯特尼,筛法，用这种方法能够筛选出全部质数。,筛选出质数方法：,1.,去,掉,1,。,2.,去,掉,2,，,3,，,5,，,7,倍数,（,2,，,3,，,5,，,7,除外,）。,3.,继,续去掉,其余质数倍数,。,第16页,1.,从教材课后习题中选取；,2.,从课时练中选取。,课后作业,第17页,
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