乘法分配律及简单应用

乘法分配律及其应用,冀教2011课标版四年级下册,抚顺市新抚区千金小学任秀敏,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,乘法交换律：,乘法结合律：,ab=ba,（ab）c=a（bc）,温故而知新,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,2594,怎样计算简便怎样算，说说运用了什么运算定律。,=2549,=1009,=900,乘法交换律,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,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,1252584,怎样计算简便怎样算，说说运用了什么运算定律。,=（1258）（254）,=1000100,=100000,乘法交换律和结合律,（3+2）434+242(11+9)112+92(20+4)5205+45,算一算：,=20,=20,=40,=40,=120,=120,你发现了什么？,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,你从图中获取了哪些有用的数学信息？,5,层,12块,9块,两扇屏风一共有多少块玻璃？,两扇玻璃屏风,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,5,层,12块,9块,有两扇5层的玻璃屏风，左边一扇每层有12块玻璃，右边一扇每层有9块玻璃。两扇屏风一共有多少块玻璃？,自己试着计算，再说一说你是怎样想的。,（3+2）434+242(11+9)112+92(20+4)5205+45,从刚才的计算中，你发现了什么？,=,=,=,两个数的和乘一个数，等于两个加数分别乘这个数，再相加。,这叫乘法分配律。,游戏：交朋友,（80+20）4,804+204,（a+100）5,a5+1005,（42+45）,=,=,=,这样的等式能写完吗？写不完，怎么办呢？,用字母表示是：,（a+b）c,ac,+,bc,a（b+c）_,ab+ac,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,填一填,1.（12+40）3=3+32.7820+7822=（+）78,12,40,20,22,乘法分配律可以正着用，也可以反着用！,1.下面哪些算式是正确的？正确的画“”，错误的画“”。56（19+28）=5619+28（）32（73）=327+323（）6464+3664=（64+36）64（）,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,乘法分配律,2.,（2+10）25=225+1025,3.一张桌子的售价是65元，一把椅子的售价是30元。买3套这样的桌椅一共需要多少元？,（65+30）3,=953,=285（元）,653+303,=195+90,=285（元）,你能用两种方法计算吗？,答：买3套这样的桌椅一共需要285元。,（1）3853+5362,（2）（25+8）4,用乘法分配律能使一些计算简便