原式=1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)=5/6原式=(1+2+3+4+……+2000)/2000=[(1+2000)*2000/2]/2000=2001/2 甲数=(496.1/11)=45.1
