Actual interview brainteaser at a top flight shop

[sjfan]

But you can't control when you win. Okay, say you win the first 2 rounds, you got $142.87 now. You lose the next round, you got $114.29 left. You lose again, you got $85.71 left. You win the next round and thus the game, but your purse of $85.71 means that even if you bet it all, you still can get to the goal of $200.

This is even more apparent if your coin out come is head, tail, head, tail, head. You'll be +14.29, -28.58, +14.29, -28.58 + 14.29 < 100.

Quote from tman:

1st win $14.29 + 2nd win 2 x $14.29= $28.58 + 3rd win 2 x $28.58= $57.16

$14.29 + $28.58 + $57.16 = $100.03

 

[AyeYo]

Quote from AyeYo:

Did you mean you'll lose on the second TAILS?

I agree with the guy that said wait for the first two heads to come out, all in on the third. 50/50 odds (which is the best you can do with a coin toss) and you're guaranteed the extra $100 if you win the game.

 

[sjfan]

OOPS

CORRECTION: You lose on the 3rd TAIL!!!

Sorry about the typo.

Quote from AyeYo:

Did you mean you'll lose on the second TAILS?

 

[AyeYo]

Quote from sjfan:

OOPS

CORRECTION: You lose on the 3rd TAIL!!!

Sorry about the typo.

Now I definitely agree with what I just posted.

 

[sjfan]

I just posted a quick correction since I misstated the loss condition: you lose on the 3rd tail.

You can't guarantee to win the game (in the terms of getting three heads). But you can guarantee to get the payoff if you win.

The problem isn't about how to get win the game (you can't). It's about how to structure your bet to get your desired payoff.

Quote from AyeYo:

I agree with the guy that said wait for the first two heads to come out, all in on the third. 50/50 odds (which is the best you can do with a coin toss) and you're guaranteed the extra $100 if you win the game.

 

[sjfan]

indeed it does

Quote from FreeMarkets:

So would the wager amount change depending on circumstance?

 

[AyeYo]

Quote from sjfan:

The problem isn't about how to get win the game (you can't). It's about how to structure your bet to get your desired payoff.

Exactly. And since it's a coin toss, the best you can do is 50/50 - hence the above suggestion.

 

[sjfan]

I think you are missing the point (or I'm explaining it badly). The point is to figure out how to bet so that if you win the game, you are guaranteed to double the game.

So, you never want to be in a situation that you've won the game, but you haven't made $100 on top of your initial stake.

There is a solution to this problem.

Quote from AyeYo:

Exactly. And since it's a coin toss, the best you can do is 50/50 - hence the above suggestion.

 

[Anaconda]

Quote from sjfan:

OOPS

CORRECTION: You lose on the 3rd TAIL!!!

Sorry about the typo.

Before you clarified that was a brain teaser of monstrous proportion as I was trying to figure WTF the rules are.

 

[Anaconda]

Quote from AyeYo:

Exactly. And since it's a coin toss, the best you can do is 50/50 - hence the above suggestion.

He stated to devise a strategy. For example, if you got 11 versus 011 or 0011. Betting $50 each time would not make sense.