分数简便计算规律 x x 3(乘法交换律) ( - )x27(乘法分配律) = x 3 x =x27 - x27 =2x =24 = =4 87x(乘法分配律) - x(乘法分配律逆向定律) =(86+1)x =x(1-) =86x+1x =x =3 = x 4 x(乘法结合律) x16x(乘法交换律) =x(4 x) =xx16 =x3 =3x16 = =48