问:20+19+18+17+16+15+14+13+12+11答:20+19+18+17+16+15+14+13+12+11=19+11+18+12+17+13+16+14+15+20=30+30+30+30+35=30×4+35=120+35=155
20+19+18+17+16+15+14+13+12+11=(20+11)+(19+12)+(18+13)+(17+14)+(16+15)=31×5=155