可爱小鑫鑫8 ,
1/3+1/15+1/35+1/63+1/99
=1/3+(1/3-1/5)+(1/5-1/7)+(1/7-1/9)+(1/9-1/11)
=1/3+1/3-1/11
=2/3-1/11
=19/33