The World's Most Difficult Logic Puzzle
posted by Calvin
- July 11 2009 02:51:31 AM
Three gods A , B , and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks falsely, whether Random speaks truly or not should be thought of as depending on the flip of a coin hidden in his brain: if the coin comes down heads, he speaks truly; if tails, falsely. Your task is to determine the identities of A , B , and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer in their own language, in which the words for yes and no are “da” and “ja”, in some order. You do not know which word means which.
You can read the solution in chapter 29 of Boolos's book Logic, Logic, and Logic, published in 1998 by the Harvard University Press. But don't give up so easily!
Since it is too difficult, I have posted the solution below.
You can read the solution in chapter 29 of Boolos's book Logic, Logic, and Logic, published in 1998 by the Harvard University Press. But don't give up so easily!
Since it is too difficult, I have posted the solution below.
Reply by admin
- July 14 2009 07:49:06 AM
Wow, this seems hard! Give me a couple days to think about it :)
Reply by sandra
- July 27 2009 11:04:54 AM
whats the answer???????
Reply by FriedPotato
- September 16 2009 10:25:42 AM
I'm thinking of a solution (refer to "a Liar OR a Truth teller")
Ask A: "If I ask the two other gods if you were False, would they say "da" or "ja"?"
A's answer: -If da, he is either True or Random.
-If ja, he is either False or Random.
(Da and Ja are determined by B)
Ask B: "If I ask the two other gods does da mean yes, would they say "da" or "ja"?"
B's answer: -If B is Truth (or Random on heads), and if he says da, then da means yes.
-If B is False (or Random on tails), and if he says ja, then da also means yes. So da always means yes and ja always means no.
Ask C: "If I ask the other two gods are any of the other two gods Random, will they say "da" or "ja"?"
C's answer: -If he says da he is True.
-If he says ja he is either False or Random.
Alright. Am I close?
Ask A: "If I ask the two other gods if you were False, would they say "da" or "ja"?"
A's answer: -If da, he is either True or Random.
-If ja, he is either False or Random.
(Da and Ja are determined by B)
Ask B: "If I ask the two other gods does da mean yes, would they say "da" or "ja"?"
B's answer: -If B is Truth (or Random on heads), and if he says da, then da means yes.
-If B is False (or Random on tails), and if he says ja, then da also means yes. So da always means yes and ja always means no.
Ask C: "If I ask the other two gods are any of the other two gods Random, will they say "da" or "ja"?"
C's answer: -If he says da he is True.
-If he says ja he is either False or Random.
Alright. Am I close?
Reply by Calvin
- October 15 2009 03:20:21 AM
FriedPotato- I don't even know. Search wikipedia. It's there.
Reply by 21eyes
- March 25 2011 12:04:22 PM
Is it ask the A if da is yes, then ask B if da is yes, then ask C if da is yes. By seeing if C fliped heads or tails you can see if he lied or not. By that you can tell what the other 2 are.
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