1/10*10+1/11*11+1/12*12+……+1/1000*1000
>1/10*11+1/11*12+1/12*13+……+1/1000*1001
=1/10-1/11+1/11-1/12+……+1/1000-1/1001
=1/10-1/1001>1/10-1/100=0.09；
1/10*10+1/11*11+1/12*12+……+1/1000*1000