Majority Rules

[BMAD]

In an presidential election between Bipa and Viktor, the winning candidate Bipa received n+k votes, whereas Viktor has received n votes. (n and k are positive integers.) If ballots are counted in a random order, what is the probability that Bipa's accumulating count will always lead his opponent's, and why?

[harey]

We already had this problem, something like drawing two different fruits from a handbag. I just cannot locate it.

http://en.wikipedia.org/wiki/Bertrand%27s_ballot_theorem

Edited March 15, 2014 by bonanova
spolier