1、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,*,1,、在,2,、,3,、,5,、,8,、,10,、,12,、,25,、,40,这几个数中,,40,的因数有几个?,5,的倍数有几个?,复习:,2,、在,6,、,10,、,12,、,15,、,18,、,20,这几个数中,哪些数是,2,的倍数?哪些数是,5,的倍数?,40,的因数有,2,,,5,,,8,,,10,,,40,。,5,的倍数有,5,,,10,,,25,,,40,。,2,的倍数有,6,,,10,,,12,,,18,,,20,。,5,的倍数有,10,,,15,,,20,。,1,2,、,5,的倍数的特征,
2、第一课时,2,座位号是多少的同学应该从双号入口进。,座位号是,2,,,4,,,6,,,8,,,2,的倍数的特征,3,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84
3、85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,2,的倍数,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,8
4、5,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,4,2,=1,2,4,=2,2,6,=3,2,8,=4,2,10,=5,2,12,=6,2,这些数都是,2,的倍数。你发现,2,的倍数有什么特征?,个位上是,0,,,2,4,,,6,,,8,的数都是,2,的倍数。,5,自然数中,是,2,的倍数的数叫做,偶数,(,0,也是偶数),不是,2,的倍数的数叫做,奇,(j),数,。,1,2,3,4,5,6,7,2,4,6,8,10,12,14,2,2,的倍数的数,6,自然数中,是,2,的倍数的数叫做偶数(,0,也是偶数),不是,2,的倍数的数叫做奇数。,自然数
5、奇数,偶数,不能被,2,整除的数,个位上是,1,,,3,,,5,,,7,,,9,。,能被,2,整除的数,个位上是,0,,,2,,,4,,,6,,,8,。,7,最小的偶数是几?有没有最大的偶数?,最小的奇数是几?有没有最大的奇数?,最小的偶数是,0,,没有最大的偶数。,最小的奇数是,1,,没有最大的奇数。,考 考 你,8,下列数中,哪些是奇数,哪些是偶数?,33 98 355 988 0 123,3678 8089 1000 655 5656 881,奇数有:,33,,,355,,,123,,,8089,,,655,,,881,。,偶数有:,98,,,988,,,0,,,3678,,,1000
6、5656,。,9,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,
7、100,5,的倍数,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,10
8、0,5,的倍数的特征,10,5,的倍数有,1,5,=5,2,5,=10,3,5,=15,4,5,=20,5,5,=25,6,5,=30,个位上是,5,或,0,的数,是,5,的倍数。,11,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?,24 35 67 90 99 15,60 75 106 130 521 280,2,的倍数:,24,,,90,,,60,,,106,,,130,,,280,。,5,的倍数:,35,,,90,,,15,,,60,,,75,,,130,,,280,,,既是,2,的倍数也是,5,的倍数:,90,,,60,,,130,,,280
9、做完这道题,你有什么发现?,12,既是,2,的倍数也是,5,的倍数:,90,,,60,,,130,,,280,。,个位上是,0,的数,既是,2,的倍数也是,5,的倍数。,13,思考:,奇数,+,偶数,=,();,奇数,+,奇数,=,();,偶数,+,偶数,=,()。,奇 数,偶 数,偶 数,14,食品店运来,85,个面包,如果每,2,个装一袋,能正好装完吗?如果每,5,个面包装一袋,能正好装完吗?为什么?,15,数学游戏,16,3,的倍数的特征,第,2,课时,17,在左表中找出,3,的倍数,并做上记号。,3,的倍数的特征,18,观察,3,的倍数,你发现了什么?与同学说一说。,19,3,的
10、倍数的数,1,2,3,4,5,6,7,3,3,6,9,12,15,18,21,把,3,的倍数的各位上的数相加,看看你有什么发现,?,20,3,的倍数的数,1,2,3,4,5,6,7,3,3,6,9,12,15,18,21,1+2=3,1+5=6,1+8=9,2+1=3,12,15,18,21,个位上的数不是,3,的倍数,但各位数的和:,3,,,6,,,9,是,3,的倍数。,21,3,的倍数的数,一个数各位上的数的和是,3,的倍数,这个数就是,3,的倍数。,3,13=39,3,23=69,3+9=12,6+9=15,22,23,1,、下列数中,3,的倍数,有,_,。,14 35 45 100 3
11、32 876 74 88,45,,,876,一个数各位上的数的和是,3,的倍数,这个数就是,3,的倍数。,24,2,、既是,2,和,5,的倍数,又是,3,的倍数的最小三位数是多少?,最小三位数是:,120,个位上是,0,的数,既是,2,的倍数也是,5,的倍数。,三位数应该是,几百几十,要求最小三位数,三位数应该是,一百几十,各位上的数的和是,3,的倍数,这个数就是,3,的倍数。,25,选出两个数字组成一个两位数,分别满足下面的条件。,(,1,)是,3,的倍数。,(,2,)同时是,2,和,3,的倍数。,(,3,)同时是,3,和,5,的倍数。,(,4,)同时是,2,、,3,、,5,的倍数。,26,






