如果我没算错的话题目第四项应该是7/12
1+1/2-5/6+7/12-9/20+11/30-13/60
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=1-1/7
=6/7