《整数乘法运算定律推广到小数》教学课件

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,*,整数乘法运算定律推广到小数,人教版五年级上册第一单元,小数乘法,乘法交换律：,两个数相乘，交换因数的位置，它们的积不变。,64,4,4,64,乘法结合律：,三个数相乘，先把前两个数相乘，,再同第三个数相乘；或者先把后两个,数相乘，再同第一个数相乘，它们的,积不变。,（,25,4,）,64,=,25,（,4,64,）,乘法分配律：,两个数的和同一个数相乘，可以,把两个加数分别同这个数相乘，再把,两个积相加，结果不变。,15,(100,3)=15,100,15,3,1.,观察下面每组的两个算式，它们有什么关系？,=,=,=,整数乘法的交换律、结合律和分配律，对于小数乘法同样适用。,2.,简便计算,(1)0.25,4.78,4,(1)0.25,4.78,4,0.25,4,4.78,1,4.78,4.78,（乘法交换律）,凑整,试一试：简便计算,38.7,0.125,80,38.7,0.125,80,38.7,(0.125,80),38.7,10,387,（乘法结合律）,试一试：简便计算,50,0.8,0.04,1.25,0.02,250,50,0.8,0.04,1.25,0.02,250,(50,0.02),(1.25,0.8),(0.04,250,),1,1,10,10,(2)0.65,202,0.65,(200,2),0.65,200,0.65,2,130,1.3,131.3,（乘法分配律）,2.,简便计算,(2)0.65,202,3.5,103,3.5,(100,3),3.5,100,3.5,3,350,10.5,360.5,试一试：简便计算,3.5,103 4.25,9.9,4.25,9.9,4.25,(10,0.1),4.25,10,4.25,0.1,42.5,0.425,41.075,用简便方法算下面各题,2.5,24 0.25,32,0.125,3.7,99 6.8,101,6.8,思考题,(1)3.6,4.7,0.36,51,36,0.02,(2)1.2,3.8,2.4,1.9,4.8,0.6,