如果最后一个是73.75：
26.25+73.75*0.35+0.65*73.75=26.25+73.75*(0.35+0.65)
=26.25+73.75*1
=100
如果最后一个是73.5：
26.25+73.75*0.35+0.65*73.5=26.25+73.75*0.35+0.65*（73.75-0.25）
=26.25+73.75*0.35+0.65*73.75-0.65*0.25
=26.25+73.75*（0.35+0.65）-0.1625
=100-0.1625
=99.8375