资源描述
,3,探索活动：,3,的倍数的特征,买哪一包糖果，可以正好分给家里的三个孩子,呢,？,75,颗,56,颗,正好分给三个孩子是找,3,的倍数。,情境导入,买哪一包糖果，可以正好分给家里的三个孩子,呢,？,56,是,2,的倍数，,75,是,5,的倍数。,谁是,3,的倍数呢？,情境导入,75,颗,56,颗,我们研究了,2,，,5,的倍数的特征，说一说，,3,的倍数有什么特征呢？,我猜个位上是,3,，,6,或,9,的数是,3,的倍数。,不一定，,13,就不是,3,的倍数。,探究新知,我们研究了,2,，,5,的倍数的特征，说一说，,3,的倍数有什么特征呢？,探究新知,我们用乘法算式找一找,3,的倍数，它们个位上的数有什么规律？,31,3,，,个位上的数没什么规律啊,我们研究了,2,，,5,的倍数的特征，说一说，,3,的倍数有什么特征呢？,探究新知,32,6,，,33,9,，,34,12,，,310,30,35,15,，,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,请你在百数表中接着圈出,3,的倍数，你发现了什么？,我发现,3,的倍数都在几条斜线上，个位上、十位上的数单独看都没有什么规律。,请你在百数表中接着圈出,3,的倍数，你发现了什么？,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,请同学们认真思考一下，在一条斜线上相邻的两个数，你能发现什么？,请同学们认真思考一下，在一条斜线上相邻的两个数，你能发现什么？,在一条斜线上相邻的两个数,(,整十数除外）,，个位上多,1,、十位上就少,1,，但是十位上的数,字,加个位上的数,字,的和是一样的。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,3,的倍数,各个数位上的数字和,发现,试着算一算这些数各个数位上的数字之和有什么规律。,12,15,18,21,24,1+2,3,1+5,6,1+8,9,2+1,3,2+4,6,3,的倍数的各个数位上的数字之和是,3,的倍数。,其他,3,的倍数也有这样的规律吗？,一个数各个数位上的数字之和是,3,的倍数，这个数就是,3,的倍数。,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,你有什么发现？,你发现的规律对三位数、四位数成立吗？找几个数来检验一下。,3,274,822,，,822,是,3,的倍数，,8+2+2,12,2016,年开了奥运会，,2+0+1+6=9,，是,3,的倍数，,2016=3672,，确实是,3,的倍数，太神奇啦！,3,65,195,，,195,是,3,的倍数，,1+9+5,15,这几个数各个数位上的数字之和是,3,的倍数。,一个数各个数位上的数字之和是,3,的倍数，这个数就是,3,的倍数。,根据上面的发现，在下面的数中圈出,3,的倍数，并与同伴交流。,5+3,8,8+7,15,3+6,9,6+5,11,6+0,6,1+2+8,11,4+5+3,12,归 纳,3,的倍数的特征：,一个数各个数位上的数字之和是,3,的倍数，这个数就是,3,的倍数。,1.,请将编号是,3,的倍数的气球涂上颜色，并与同伴交流你是怎么判断的。,3+6,9,1+7,8,5+4,9,7+1,8,4+5,9,4+8,12,巩固练习,【,选自教材,P36,练一练 第,1,题,】,2.,分别在 里填上一个数字，使这个两位数是,3,的倍数。,2,5,3,0,7,1,2,4,2,7,1,5,4,5,7,3,6,3,9,3,3,6,0,9,0,2,5,7,8,7,【,选自教材,P36,练一练 第,2,题,】,7+11=18,11,3.,选出两个数字组成一个两位数，分别满足下面的条件。,30,，,45,或,54,；,(2)30,，,54,；,(3)45,，,30,；,(4)30,。,【,选自教材,P36,练一练 第,3,题,】,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,4.,在百数表中找出,9,的倍数，并涂上颜色。,（,1,）观察,9,的倍数，它们有什么特征？,9,的倍数的特征：,每个数各个数位上数字之和都是,9,的倍数。,【,选自教材,P36,练一练 第,3,题,】,（,2,）这些数的排列有什么特征？,9,的倍数,9,，,18,，,，,81,排在一条斜线上，,90,，,99,排在一条斜线上。,4.,在百数表中找出,9,的倍数，并涂上颜色。,【,选自教材,P36,练一练 第,3,题,】,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,（,3,）如果左表扩充到,200,，并找出,99,后面是,9,的倍数的数，它们将在表中的什么位置？做一做，检验你的答案。,4.,在百数表中找出,9,的倍数，并涂上颜色。,【,选自教材,P36,练一练 第,3,题,】,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,（,3,）将表格扩充到,200,，发现,9,的倍数,90,，,99,，,108,，,117,，,，,171,排在一条斜线上，,180,，,189,，,198,排在一条斜线上。,课堂小结,一个数各个数位上的,数字之和是,3,的倍数,，这个数就是,3,的倍数。,3,的倍数特征：,
展开阅读全文