Question

二分之一减去六分之一减去十二分之一减去二十分之一减去三十分之一减去四十二分之

Answer 1

1/2-1/6-1/12-1/20-1/30-1/42

=1/2-(1/6+1/12+1/20+1/30+1/42)

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

=1/2-(1/2-1/7)

=1/2-1/2+1/7

=1/7