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小数的加法和减法,第,6,课时 整数加法运算定律推广到小数,一、复习旧知,7,2,42,28,158,100,200,300,（,72,28,）,（,42,158,）,在计算时应用了,什么运算定律？,用到了加法交换律,和加法结合律。,怎样简便就怎样算。,3,.,2,0,.,5 0,.,5,3,.,2,（,4,.,7,2,.,6,）,7,.,4 4,.,7,（,2,.,6,7,.,4,）,=,=,二、探究新知,下面每组算式两边的结果相等吗？,整数加法的交换律、结合律对小数加法同样适用。,应用运算定律，,可以使一些小数,计算更简便。,二、探究新知,8,.,51,3,.,4,0,.,09,11,.,91,0,.,09,计算,0,.,6,7,.,91,3,.,4,0,.,09,。,12,4,8,（,0,.,6,3,.,4,）,（,7,.,91,0,.,09,）,12,0,.,6,7,.,91,3,.,4,0,.,09,0,.,6,7,.,91,3,.,4,0,.,09,你准备怎样计算？,我是这样计算的。,小伟,我按从左往右,的顺序计算。,小丽,二、探究新知,0,.,6,7,.,91,3,.,4,0,.,09,4,8,0,.,6,3,.,4,7,.,91,0,.,09,12,（,0,.,6,3,.,4,）,（,7,.,91,0,.,09,）,小伟在计算时应用,了什么运算定律？,应用了加法交换律,和加法结合律。,（,1,）,6,.,7,4,.,95,3,.,3,6,.,7,4,.,95,（,2,）（,1,.,38,1,.,75,）,0,.,25,（,）,三、知识运用,3,.,3,1,.,38,1,.,75,0,.,25,这样算应用了,加法交换律。,这样算应用了,加法结合律。,1.,在 里填上适当的数。,三、知识运用,1,.,88,（,2,.,3,3,.,7,）,1,.,88,6,7,.,88,1,.,88,2,.,3,3,.,7,（,1,3,.,7,4,.,3,）,（,0,.,98,0,.,02,）,18,1,19,13,.,7,0,.,98,0,.,02,4,.,3,2.,计算下面各题，怎样简便就怎样计算。,三、知识运用,5,.,17,1,.,8,3,.,2,5,.,17,（,1,.,8,3,.,2,）,5,.,17,5,0,.,17,4,.,02,3,.,5,0,.,98,4,.,02,0,.,98,3,.,5,5,3,.,5,1,.,5,3.,计算下面各题，怎样简便就怎样计算。,三、知识运用,6,.,55,5,.,80,2,.,20,14,.,55,（元）,6,.,55,（,5,.,80,2,.,20,）,答：一共,14,.,55,元,。,6,.,55,8,4.,开心超市。,请你提出一,个数学问题,并解答。,火腿肠、饼干和,牛奶一共多少元？,27,.,60,6,.,55,13,.,40,5,.,80,2,.,20,22,.,25,蛋糕,火腿肠,口香糖,饼干,牛奶,酸奶,
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