Question

1乘2分之2005加2乘3分之2005加3乘4分之2005……加2004乘2005分之2005等于多少

Answer 1

1/1乘2+1/2乘3+1/3乘4+..+1/2004乘2005

=(1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/2004-1/2005)

=1-1/2005=2004/2005