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1、,3 的倍数的特征,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,下面哪些数是2的倍数？哪些数是5的倍数?哪些数既是2的倍数，也是5的倍数？ 42 35 67 90 99 15 60 75 130 521 280 6018,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（1）上表中哪些是3的倍数？把它们圈起来。,状元成
2、才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（2）横着看，圈起来的前10个数，个位分别是哪些数字。,3,6,9,2,5,8,1,4,7,0,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（2）判断一个数是不是3的倍数，只看个位行吗？,3,6,9,2,5,8,1,4
3、,7,0,3的倍数个位上可以是任意数。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,（3）斜着看，你发现了什么？,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,斜着看，3的倍数各位上的数的和都是3的倍数。,状元成才路,状元成才路,状元成才路,状元成才路,状元
4、成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,任意找几个3的倍数，把各位上的数相加，看看你有什么发现？,42,4 + 2 = 6， 6是3的倍数,78,7 + 8 = 15， 15是3的倍数,一个数各位上的数的和是3的倍数，这个数就是3的倍数。,归纳小结,2 的倍数：个位是 0、2、4、6、8,5 的倍数：个位是 0、5,3 的倍数：各位上数字之和是 3 的倍数,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才
5、路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,下面用数字卡片摆出的数字中哪些是3的倍数？在每个数后面增加一张卡片，使这个三位数成为3的倍数。,2,4,5,8,2+4=6 24是3的倍数,0,3,6,9,5+8=13 58不是3的倍数,2,5,8,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,4,7,9,6,4+7=11 47不是3的倍数,1,4,7,9+6=15 96是3的
6、倍数,0,3,6,9,智慧屋,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,1. 圈出3的倍数。,92 75 36 206 65 3051 779 99999 111 49 165 5988 655 131 222 7203,这种方法叫“弃3”法，就是先把3的倍数划去，剩下的数再相加判断。,2. 在里填一个数字，使每个数都是3的倍数。,7 42 44 65 121,2,5,8,0,3,6,9,1,4,7,1,4,7,2,5,8
7、,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,3. 下面的判断正确吗？小组间相互讨论一下。,（1）个位上是 3、6、9 的数，都是 3 的倍数。,（2）奇数都不是 3 的倍数。,（3）是 9 的倍数的数，一定是 3 的倍数。,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,4. 从下面 4 张数字卡片中取出两张组成两位数，要求分别满足下面的条件：,4,3,0,5,（1）是 3 的倍数,（2）同时是 2 和 3 的倍数,30,45,54,30,54,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,4. 从下面 4 张数字卡片中取出两张组成两位数，要求分别满足下面的条件：,4,3,0,5,（3）同时是 5 和 3 的倍数,（4）同时是 2、3、5 的倍数,30,45,30,