2018-201.8+20.18-2.018+0.008=2018(1-1/10+1/100-1/1000)+8/1000=2018*909/1000+8/1000=(1834382+8)/1000=1834390/1000=1834.39
2018-201.8+20.18-2.018+0.2018=0.2018×（10000-1000+100-10+1）=0.2018×9091=1834.5638
