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Flipping for Dollars (Posted on 2002-10-09) Difficulty: 3 of 5
We play a game as follows:

I place one dollar on the table. I repeatedly flip a coin. Each time the coin comes up heads, I double the money on the table. The first time the coin comes up tails, you take the money and the game is over.

What's a fair admission price for the game?

Would you play the game with me for $100?

See The Solution Submitted by Jim Lyon    
Rating: 3.9000 (10 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re(2): something missing | Comment 13 of 21 |
(In reply to re: something missing by Cheradenine)

wild speculation:

define the expectancy expectancy E2 as the number of
trials the games takes to reach a certain expectancy
value. in other words E2 determines how many trials
are necessary to expect on average an expectancy E
(for those trials).

E2 is really a function of cost and target expectancy:
E2(expectancy, cost). my attempt at obtaining this for
a given cost is:

find the biggest term in E(cost) which included in
E(cost) >= expectancy. E2 is then given by this biggest
term. in the case of the above problem, it turns out
that E2(0, cost) = 4^cost.

the answer to the first question is that the fair price
is

log4(x)

where you have x dollars.

the answer to the second question is, if i have
4^100 (1,606e+60) dollars or more, i would play.
  Posted by Cheradenine on 2002-10-10 08:11:14

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