The martingale betting strategy ensures that you will always win one unit of your first bet but only IF you have infinite money to back it up with. If you don’t have infinite money you’ll either walk away a little positive or lose a disastrous amount.
The strategy works when there’s even odds, for example flipping a coin for double or nothing. An example: Bet $100, if you win you walk away $100 richer, if you lose you double your next bet to $200. Winning this time means you’ve spent $300 and gained $400 and can walk away with your $100. Otherwise double your bet again to $800. Keep doubling until you eventually win and walk away richer than you started.
Problem with this betting strategy lies in your bankroll, if you run out of money before winning you will lose all you own. Otherwise you’ll win a small profit depending on what chance you take on the first bet compared to how many times you can afford to lose according to your bankroll.
If you at first don’t succeed, try twice as hard!
[pic: CC-BY-NC-ND, Daniel Dale]