Source: Credit Suisse Placement Test at IITB
You bet 1$ on a coin toss. A win gives u 1$ gain, a loss gives you a 1$ loss. The guy tossing the coin gets what he wants 80% of the time. You start with X$. Find strategy so that you always win.
Update (Dec 04, 2010)
Note that the dealer is just an employee of the casino. You can take him in your group and make an offer he cannot refuse.
Solution: Posted by Gaurav Sinha (chera) (CSE IITK 1996 Graduate, Now working at Indian Revenue Service) in comments!