The probability that the nth flip is tails is 1/2^n. The amount of money won if the nth flip is tails is 2^(n-1).
Mathematically speaking, the value of the game is:
1/2 * 1 + 1/4 * 2 + 1/8 * 4 + ...
which equals
1/2 + 1/2 + 1/2 + ...
So, mathematically speaking, the value of the game is infinite.
In practical terms, however, you'll soon be limited by the amount of money I have. (That is, there will soon come a point where I am incapable of doubling the money on the table.) So, the series ends at that point. In reality, the series only has as many terms as log2 of the money I have, and the value of the game is 1/2 that.
So, if I have about $1000, the value of the game is $5. If I have about $1,000,000, the value of the game is $10. If I have $1,000,000,000, the value of the game is $15. Even if I'm Bill Gates, the value is less than $20. |