计算有理数的题!

题目

计算有理数的题!
_1_+_1_+_1_+.+_____1_____
1*3 3*5 5*7 2003*2005

答案

=(1/2)(1-1/3)+(1/2)(1/3-1/5)+……+(1/2)(1/2003-1/2005)
=(1/2)(1-1/3+1/3-1/5+……+1/2003-1/2005)
=(1/2)(1-1/2005)
=1002/2005