Question

（1+3+5+7……+99+101）-（2+4+6……+98+100）

Answer 1

（1+3+5+7……+99+101）-（2+4+6……+98+100）

=1+(3-2)+(5-4)+----+(101-100)

=1+1+1+---+1

=51

1/(2*4)+1/(3*5)+1/(4*6).+1/(8*10)+1/(9*11)

=(1/2)*(1/2-1/4+1/3-1/5+1/4-1/6+------+1/8-1/10+1/9-1/11)

=(1/2)*( 1/2+1/3-1/10-1/11)

=(1/2)*(5/6-21/110)

=53/165