1+ (1+2)分之1+ (1+2+3)分之1+ (1+2+3+4)分之1+.(1+2+3+...100)分之1 =1+2/(1+2)*2+2/(1+3)*3+.2/(1+100)*100 =1+2(1/2-1/3+1/3-1/4+.+1/100-1/101) =1+2(1/2-1/101) =1+1-2/101 =200/101