1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+……+1/100+2/100+……+99/100=(1/2)+(1/3+2/3)+(1/4+2/4+3/4)+(1/5+2/5+3/5+4/5)+……+(1/100+2/100+……+99/100)=1/2+2/2+3/2+4/2+....+99/2=[(1+99)*99/2]/2=9900/4=2475
恩,太难了,楼上解答不错!