Question

2分之1+6分之1+12分之1+20分之1+.+4022030分之1?

Answer 1

2分之1+6分之1+12分之1+20分之1+.+4022030分之1

=1/1*2+1/2*3+1/3*4+……+1/2005*2006

=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/2005-1/2006)

=1-1/2006

=2005/2006