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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,第,4,课时 整数加法运算定律推广到小数,R,四年级下册,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,状元成才路,状元成才路,状元成才路,状元成才路,复习旧知,32+5=,（）,+32,两个数相加，交换加数的位置，和不变。这叫做,加法交换律,。,用字母表示为：,a,+,b,=,b,+,a,5,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,状元成才路,状元成才路,状元成才路,状元成才路,(,47+26,),+74,=,47+,(,（）,+74,),三个数相加，先把前两个数相加，或者先把后两个数相加，和不变。这叫做,加法结合律,。,用字母表示为：,（,a,+,b,）,+,c,=,b,+,（,a,+,c,）,26,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,状元成才路,状元成才路,状元成才路,状元成才路,自主探究,下面每组算式两边的结果相等吗？,3,.,2+,0.,5,0.,5+3,.,2,（4,.,7+2,.,6）+7,.,4,4,.,7+（2,.,6+7,.,4）,=,=,你有什么发现？,发 现,整数加法的,交换律,、,结合律,对小数加法同样适用。,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,状元成才路,状元成才路,状元成才路,状元成才路,计算,0.6+7.91+3.4+0.09,方法,1,0.6+7.91+3.4,+,0.09,=,8.51+3.4+0.09,=,11.91+0.09,=12,有更简单的方法吗？,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,状元成才路,状元成才路,状元成才路,状元成才路,方法,2,0.6+7.91+3.4+0.09,+,4,+,8,(,0.6+3.4,),+,(,7.91+,0.09,),=4+8,=12,应用了加法,交换律,和加法,结合律,。,小伟在计算时应用了什么运算定律？,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,状元成才路,状元成才路,状元成才路,状元成才路,观,察,两种方法有什么相同点和不同点。,0.6+7.91+3.4,+,0.09,=,8.51+3.4+0.09,=,11.91+0.09,=12,0.6+7.91+3.4,+,0.09,(,0.6+3.4,),+,(,7.91+,0.09,),=4+8,=12,结果相同,从左往右的顺序依次计算的,运用了加法交换律和结合律,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,状元成才路,状元成才路,状元成才路,状元成才路,做,一,做,1.,在 里填上适当的数。,(,1,),6.7+4.95+3.3,6.7+4.95,3.3,(2)(,1.38+1.75,)+,0.25,+(,+,),1.38,1.75,0.25,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,状元成才路,状元成才路,状元成才路,状元成才路,2.计算下面各题，怎样简便就怎样计算。,1.88+,2.3+3.7,=1.88+,(,2.3+3.7,),=1.88+6,=7.88,13.7+,0.98+0.02+4.3,=,(,13.7+4.3,),+,(,0.98+0.02,),=18+1,=19,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,状元成才路,状元成才路,状元成才路,状元成才路,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,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,状元成才路,状元成才路,状元成才路,状元成才路,结,小,纳,归,在小数四则混合运算中要仔细观察每个数的特征，注意数与数之间的关系及每个数前面的运算符号，恰当地运用加法,交换律,、,结合律,及,减法的运算性质,进行简便运算，把能“,凑整,”的两个或两个以上的数先加、减。,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,状元成才路,状元成才路,状元成才路,状元成才路,巩固深化,1.,口算。,0.384+0.37+2.63=,5.28+3.43+0.72=,1.29+3.6+0.71+6.4=,3.384,12,9.43,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,状元成才路,状元成才路,状元成才路,状元成才路,2.,看谁算得快。,35.6+58.9+22.4,=35.6+22.4+58.9,=58+58.9,=116.9,59.7,-,12.12,-,5.88,=59.7,-,(,12.12+5.88,),=59.7,-,18,=41.7,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,状元成才路,状元成才路,状元成才路,状元成才路,2.8+1.37+7.2+42.63,=,(,2.8+7.2,),+,(,1.37+42.63,),=10+44,=54,(,21.34+28.68,),+12.66,=21.34+12.66+28.68,=34+28.68,=62.68,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,状元成才路,状元成才路,状元成才路,状元成才路,3.,小华在文具店买下面的文具，一共用了多少元？,8.9,元,3.6,元,6.4,元,1.1,元,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,状元成才路,状元成才路,状元成才路,状元成才路,方法一：,8.9+3.6+6.4+1.1,=12.5+6.4+1.1,=18.9+1.1,=20,方法一：,8.9+3.6+6.4+1.1,=,（,8.9+1.1,）,+,（,3.6+6.4,）,=10+10,=20,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,状元成才路,状元成才路,状元成才路,状元成才路,课堂小结,发 现,整数加法的,交换律,、,结合律,对小数加法同样适用。,3,.,2+,0.,5,0.,5+3,.,2,（4,.,7+2,.,6）+7,.,4,4,.,7+（2,.,6+7,.,4）,=,=,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,状元成才路,状元成才路,状元成才路,状元成才路,1.,完成,P77,第,1,2,题；,2.,完成练习册本课时的习题。,课后作业,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,
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