1乘3分之2+3乘5分之2+5乘7分之2+7乘9分之2+……+95乘97分之2+97乘99分之2
=1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+……+1/95-1/97+1/97-1/99
=1-1/99
=98/99