Read this somewhere and dunno the answer...
How do you have a fair coin toss over the phone?
Don't read comments till you've tried!!! Also try using anything...not just coins. Maybe guessing the number in your head, or which of your hands has a stone, who's going to hang up first...
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8 comments:
What the heck does the question mean?
Put the phone on the table. Then flip a coin over it?
Or, get yourself an iPhone which has an application that allows you to flip coins, roll dice, or pull random cards.
Or, perhaps you are talking to someone on the phone. Call "same" or "different" instead of "heads/tails." Then both of you flip a coin and reveal the result at the same time. If both end up saying the same thing....well, the rest of this is obvious.
Also, Joey, how do I post on your blog? Do you need to add me as a team member or something?
well, in response to the non-smart allecky comment =P...The idea is that it is still possible to cheat in that scenario. If you hear the other person calling heads, you switch to tails (If you called different) since "exact timing" is not possible.
perhaps i killed the riddle...but the answer seems way too complicated...
The mathematical abstraction of the statistics of coin flipping is described by means of the Bernoulli process; a single flip of a coin is a Bernoulli trial. In the study of statistics, coin-flipping plays the role of being an introductory example of the complexities of statistics. A commonly treated textbook topic is that of checking if a coin is fair.
[edit] Coin flipping in telecommunications
There is no fair way to use a true coin flip to settle a dispute between two parties over distance — for example, two parties on the phone. The flipping party could easily lie about the outcome of the toss. In telecommunications and cryptography, the following algorithm can be used:
Party A chooses two large primes, either both congruent to 1, or both congruent to 3, mod 4, called p and q, and produces N = pq; then N is communicated to party B, but p and q are not. It follows N will be congruent to 1 mod 4. The primes should be chosen large enough that factoring of N is not computationally feasible. The exact size will depend on how much time party B is to be given to make the choice in the next step, and on party B's expected resources.
Party B calls either "1" or "3", a claim as to the mod 4 status of p and q. For example, if p and q are congruent to 1 mod 4, and B called "3", B loses the toss.
Party A produces the primes, making the outcome of the toss obvious; party B can easily multiply them to check that A is being truthful.
this is only something computer programmers/mathemticians would think about....
You are absolutely correct. "Exact Timing" is not possible. To be correct to an infinite decimal place is not possible. Being correct to less than 10E-12 seconds is not possible for humans either. But what's the point of being so theoretical?
On a practical basis, the average human reaction time to sound is 140 milliseconds, so 0.14 seconds. That's quoting the wikipedia page here http://en.wikipedia.org/wiki/Reaction_time, and that's just to hear the sound. Then you have to add time to comprehend and then add time to say your own selection.
Wow, if you can change what you're about to say just like that, you must be a borg from the future.
No kidding, you'd also always win at rock-papers-scissors! See them choosing rock, and switch to paper. How sweet would that be? You can take down the annual U.S. Roshanbo (fancy name for rock/paper/scissors) tournament every year and win $100,000 from ESPN. It'd be the easiest 6-figure job EVER!!!!
Give me some credit; my way works somewhere around 99.9% rating (I'm assuming borg from future is a 0.1% possibility, that's probably an overestimation).
That said, sure you could look for the theoretical solution. The perfect solution. I'll continue pondering this puzzle during my more boring moments also.
Holy shit.... alright Choe, you will.
For some reason, I thought there had to be coins involved.
lol actually me and ktao were trying to think of that since Fogel told us about that solution at IMSA...did you google or just know?
Choe got it from wikipedia, methinks. Try the "Coin Flippin" article.
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