3/2-5/6+7/12-9/20+11/30-13/42+…+197/9702-199/9900
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)...+(1/98+1/99)-(1/99+1/100)
=1-1/100(中间的部分全都约去了）
=99/100