欢迎来到奥数游乐场巧算乘除法乘法交换律:a b = b a乘法结合律:a b c = a (b c)乘法分配律: (a + b) c = a c + b c由此可以推出: a b + a c = a (b +c) (a-b) c = a c b c除法的性质: a b c = a c b = a (b c)例1 ,计算 (1 )25 5 64 125 (2 )56 165711 分析:(1 )在计算乘、除法时,我们通常可以运用2 5 、4 25 、8 125 来进行巧妙的计算! (2 )运用除法的性质,带着符号“搬家”。解:(1 )25 5 64 125 = 25 5 2 4 8 125 = ( 25 4 ) ( 5 2 ) (8 125 ) = 100 10 1000 = 1000 000 (2 )56 165711 = (567 ) (16511 ) = 8 15 =120随堂练习1 计算: (1 )25 96 125 = 25 4 8 3 125 = ( 25 4 ) ( 8 125 )3 = 100 1000 3 = 300 000(2 )77 777 99 99911 111