2023年五年级数学上册三倍数与因数第3课时探索活动：3的倍数的特征课件北师大版

,第,3,课时 探索活动：,3,的倍数的特征,北师大版五年级上册,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？,新课导入,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。,31,3,，,32,6,，,33,9,，,34,12,，,35,15,，,310,30,，,个位上的数没什么规律啊,推进新课,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？,你知道吗？这些数各个数位上的数字之和都是,3,的倍数。,3,的倍数,各个数位上的数字和,发现,12,1,2,3,3,的倍数的各个数位上的数字之和是,3,的倍数。,15,1,5,6,18,1,8,9,21,2,1,3,24,2,4,6,是这样吗？我找几个数看看：,2016,年开了奥运会，,2+0+1+6=9,，是,3,的倍数，,2016=3,672,，确实是,3,的倍数，太神奇啦！,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。,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。,随堂演练,2.,分别在 里填上一个数字，使这个两位数是,3,的倍数。,2,5,3,0,7,1,2,4,2,7,1,5,4,5,7,3,6,3,9,3,3,6,0,9,0,2,5,7,8,7,3.,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,。,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的和都是,9,的倍数。,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,4.,在百数表中找出,9,的倍数，并涂上颜色。,（,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。,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。,（,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。,（,3,）将表格扩充到,200,，发现,9,的倍数,90,，,99,，,，,171,排在一条斜线上，,180,，,189,，,198,排在一条斜线上。（检验略）,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。,