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1、龙山乡十里塘小学 张立强,简便运算,加法交换律: a+b=b+a,返,加交,加结,乘交,乘结,乘分,减,除,搬,总,加法结合律:(a+b)+c=a+(b+c),返,加交,加结,乘交,乘结,乘分,减,除,搬,总,乘法交换律: ab=ba,返,加交,加结,乘交,乘结,乘分,减,除,搬,总,乘法结合律: (ab)c=a(bc),返,加交,加结,乘交,乘结,乘分,减,除,搬,总,乘法分配律:(a+b)c=ac+bc,返,加交,加结,乘交,乘结,乘分,减,除,搬,总,减法的性质:abc=a(b+c),返,加交,加结,乘交,乘结,乘分,减,除,搬,总,除法的性质:abc=a(bc) ( b、c0),返,加
2、交,加结,乘交,乘结,乘分,减,除,搬,总,加法交换律: a+b=b+a,加法结合律:(a+b)+c=a+(b+c),乘法交换律:ab=ba,乘法结合律:(ab)c=a(bc),乘法分配律:(a+b)c=ac+bc,减法的性质:abc=a(b+c),除法的性质:abc=a(bc),带符号搬家:a+bc=ac+b abc=acb,一、基本练习:,1、用简便方法计算: 3.4101 4.7+56+5.3+44 4001258 125-99 4 + 4 0.12542.5,二、用简便方法计算,并用字母表示出来。,38753855 abac= = = = 1000(12516) a(bc)= = =
3、=,38(7555),a(bc),3820,760,100012516,abc,816,128,9123(123+8.8) = = = 17.15(3.5 2.85) = = = =,a(b+c)=abc,91231238.8,90008.8,8991.2,17.153.5+2.85,17.15+2.853.5,203.5,16.5,a (b c)=a b+c,17.158.471.53 40001258,一个数连续减去(除以)两个数,可以用这个数减去(除以)这两个数的和(积)。,三、计算,并说说是怎样简便的?,=17.15(8.47+1.53) =17.1510 =7.15,=4000(12
4、58) =40001000 =4,2512548 =254125 8 =(254)(125 8) =100 1000 =100000 1.25(8+10) =1.25 8+1.25 10 =10+12.5 =22.5,乘法交换律乘法结合律,四、用简便方法计算,运用了那些运算定律?,乘法分配律,4,34,34,乘法分配律,乘法结合律,4,4,=,4,(,),=,4,1,=,0.25,4,=,(,0.25,4,),=,34,1,=,34,六、综合练习,能简便的用简便方法计算: 125 8 25+75-75+25 189 1.5 +0.86.5+2 56(7+8) 1258.8,七、小测试,2580.41.25 87 578298 4.381.56+0.620.44 187.711187.7,6.788.5+6.78 0.5 + 6.78 2.45 4.55,993.4 4.354.253.653.75,我能用简便方法计算,