Question

二分之一+六分之一+十二分之一+二十分之一+三十分之一+四十二分之一=?

Answer 1

=1/2+1/6+1/12+1/20+1/30+1/42

=1/(1*2)+1/(2*3)+1/(4*5)+...1/(6*7)

=1-1/2+1/2-1/3+...-1/7

=1-1/7

=6/7