=1.25×0.25×0.4×0.8=(1.25×0.8)×(0.4×0.25)=1
1.25×0.25×3.2=5/4×1/4×16/5=1
1.25*0.25*（8*0.4）=1.25*8*0.25*0.4=10*0.1=1
