1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 +······1/9900
=1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/6-1/7+...+1/99-1/100
=1-1/100
=99/100
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/110 +······1/9900
=1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/6-1/7+...+1/99-1/100
=1-1/100
=99/100