1/1乘于2+1/2乘于3+1/3乘于4+... ...+1/99乘于100,等于多少?简便运算.
问题描述：
1/1乘于2+1/2乘于3+1/3乘于4+... ...+1/99乘于100,等于多少?简便运算.
答
1/1乘于2+1/2乘于3+1/3乘于4+......+1/99乘于100
=1-1/2+1/2-1/3+……+1/99-1/100
=1-1/100
=99/1001/1乘于3+1/3乘于5+1/5乘于7+1/7乘于9+... ...+1/2008乘于2009.还有一题，做出来给你10金钱1/12+1/20+1/30+1/42+1/56+1/72+1/901/1乘于3+1/3乘于5+1/5乘于7+1/7乘于9+... ...+1/2007乘于2009.=½（1-1/3+1/3-1/5+……+1/2007-1/2009)=½(1-1/2009)=½×2008/2009=1004/2009题目自己改下1/12+1/20+1/30+1/42+1/56+1/72+1/90=1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10=1/3-1/10=3/10