乘法互换率,0.75先和0.4乘,得到0.3。0.3再和0.4相乘得到0.12
=0.25*3*0.7*0.4=0.25*0.4*2.1=0.1*2.1=0.21
=(0.75✘0.4)✘0.7=0.3✘0.7=0.21
0.75×0.7×0.4=0.75×0.4×0.7=0.3×0.7=0.21