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1、小 数 乘 法 复 习 课,孙营乡李佐小学 姜冰涛,1 文具店,0.018,0.023,0.018,0.023,0.08,0.06,0.0110,0.5,0.0110,0.1,0.5,0.110 0.150 0.0160 0.01100 0.0012000,练习一,1,5,0.6,1,2,2 小数点搬家,小数:3.15,小数点向右移动一位:,31.5,小数点向右移动两位:,315.,小数点向右移动三位:,3150.,小数点向右移1位,这个数扩大10倍,小数点向右移2位,这个数扩大100倍,小数点向右移3位,这个数扩大1000倍,小数点向右移1位,这个数扩大10倍 小数点向右移2位,这个数扩大1
2、00倍 小数点向右移3位,这个数扩大1000倍 (1.212.0)1.21012 (1.2 120.0)1.2100120 (1.2 1200.0)1.210001200,小数点向左移1位,这个数缩小10倍 小数点向左移2位,这个数缩小100倍 小数点向左移3位,这个数缩小1000倍,(1.20.12)1.210 0.12 (1.2 0.012)1.21000.012 (1.2 0.0012)1.210000.0012,12.5,125,1250,3,30,300,0.98,9.8,98,20.4,204,2040,2.48,0.248,0.0248,0.12,0.012,0.0012,0.0
3、6,0.006,0.0006,42.5,4.25,0.425,32.510= 1.43100= 1.81000= 32.510= 1.43100= 1.81000=,算一算,325,143,1800,3.25,0.0143,0.0018,3 街 心 广 场,53 50.3 0.53 0.050.3,乘数有多少个小数位,积就有多少个小数位,15,1.5,1.5,0.015,0,1,1,1,1,2,2,2,0,2,1,3,0.12,0.26,0.026,2 下面的积是几位小数位,填在括号里 2.14= ( ) 30.112.3= ( ) 0.250.01= ( ) 70.256= ( ) 1.22
4、1= ( ) 6.5410.1= ( ) 110.01= ( ) 8740.213= ( ),1,3,4,3,1,4,2,3,4 包 装,5 爬行最慢的动物,4.80.05,竖式计算一,1 看作整数,2 竖式计算,3 算出乘数的小数位,4 点上积的小数点,方法:,注意: 1 将位数多的数放在上面(方便计算) 2 在乘法,小数点不用对齐 3 竖式是要从右边对齐,竖式计算二,1.950,练习题 竖式计算,0.362.3= 3.21.5= 0.254.4= 0.0071.8,6 手拉手,简便计算,abc=(ac) b,1.251.890.8=(1.250.8) 1.89,ac+bc=(a+b) c,
5、1.85.1+8.25.1=(1.8+8.2) 5.1,ac-bc=(a-b) c,10.85.1-0.85.1=(10.8-0.8) 5.1,2.50.9990.4,(2.50.4)0.999,10.999,0.999,0.861.258,0.86(1.258),0.8610,8.6,简便计算,9. 90.99. 90.1,简便计算,(0.90.1)9.9,19.9,9.9,(0.80.08)12.5,0.812.50.0812.5,101,11,简便计算,2.50.864 0.1121.258 9.19249.1914 9.98.80.18.8 (10.8)12.5 (0.40.04)25,