27.2+2.27+2.73+0.8=（27.2+0.8）+（2.27+2.73）=28+5=33注：题目273应该是2.73
27.2+2.27+273+0.8=27.2+0.8+2.27+273=28+2.27+273=30.27+273=303.27
