1又1/3-7/12+9/20-11/30+13/42-15/56+.+197/9702-199/9900
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8+……+1/98+1/99-1/99-1/100
=1-1/100
=99/100