1、将12.5和0.25交换个位置
0.8x0.25x0.4x12.5
=0.8x12.5x0.4x0.25
2、0.8x0.25算出为10
0.8x12.5x0.4x0.25
=10x0.4x0.25
3、将0.25和10交换个位置
10x0.4x0.25
=0.25x0.4x10
4、0.25x0.4算出为0.1
0.25x0.4x10
=0.1x10
5、经过运算，最后结果为1
6、运算全过程为：
0.8x0.25x0.4x12.5
=0.8x12.5x0.4x0.25
=10x0.4x0.25
=0.25x0.4x10
=0.1x10
=1
