Why is it a dumb idea for me to go to a casino and play roulette ONLY until I double my money or break even?

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So I don’t gamble, and don’t ever indend to make it a habit.

But a friend told me to play roulette, and I would have a ~47% chance of doubling my money and , as long as I had enough money to keep doubling my stake, would have a ~95% break even if I kept going until I won and never played again.

So say I had $200k in the bank and always put my money on red

Spin 1 : $5K

Spin 2: $10K

Spin 3: $20K

Spin 4: $40k

Spin 5: $80K

Spin 6: $160k

In this scenario, I’d have a ~47% chance of winning $5k, and just a 2% chance of losing $160k?

EDIT: Although just working this out, I think I would probably put the 160k into a 4% savings account if I had it, or start off way smaller amounts e.g. $500 to reduce my chane of losing money significantly lol.

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46 Answers

Anonymous 0 Comments

Let’s assume you can make all those bets. Let’s look at the expected value:

First off: with $200K, you can only make 5 bets: having already bet $155K at that point, you only have $45K.

Over 5 bets, you have a (53%)^(5) chance of losing everything: about a 4% chance of losing $155K – an expected loss of $6.4K. Over the same 5 bets, your ~96% chance of winning $5K is less than that – so, on average, you will lose.

And that’s the problem of the “Martingale System” – it stops working as soon as you run out of money. In theory, if you have an infinite amount of money and time, and no limits to how much you can bet, it works – but in practice, there is a negative expected value and you will run out of money eventually.

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