(39.6*478-3.6)/(39.5*479+4.7)
=[(39.5+0.1)*478-3.6]/[39.5*(478+1)+4.7]
=[39.5*478+(47.8-3.6)]/[39.5*478+(39.5+4.7)]
=(39.5*478+44.2)/(39.5*478+44.2)
=1