0.125*3.2+0.125*5.8-1/8
=0.125*8*0.4+0.125*5.8-0.125
=1*0.4+0.125*5+0.125*0.8-0.125
=0.4+0.125*(5-1)+0.1
=0.4+0.5+0.1
=1