73*0.125*0.25*0.4
=(72+1)*0.125*(0.25*0.4)
=(8*9+1)*0.125*0.1
=8*9*0.125*0.1+1*0.125*0.1
=(8*0.125)*9*0.1+0.0125
=0.9+0.0125
=0.9125