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Very Hard Puzzles.


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#1 Guest: Mushroom_*

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Posted 19 July 2006 - 07:50

Hello, I have an incredibly hard puzzle to solve, here it is.

There is a prisoner, and in front of him there are two doors, one leads to freedom, the other to certain death, he doesn't know which one is which. There are two guards , guarding one door each, they know which door leads to death and freedom. One guard always lies, the other always tells the truth, the prisoner doesn't know which one lies and which one is truthful. To ensure he goes for the right door, which ONE question can he ask?
(The guards can only answer yes or no.)
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#2 Guest: kayladavies_*

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Posted 19 July 2006 - 12:03

Are you dead?
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#3 Guest: janexxx_*

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Posted 19 July 2006 - 12:52

QUOTE(kayladavies @ Jul 19 2006, 01:03 PM) View Post

Are you dead?

Well you'll know which one lies, but how will you know which is the right door?? You only have ONE question.

I know this one...the two guards know which one of them lies and which one tells the truth. Does that help?
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#4 Guest: Mushroom_*

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Posted 19 July 2006 - 12:53

If you'd looked, I've already said that.

I'll give you a clue, ask the guard about the other guard.
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#5 bobifier

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Posted 19 July 2006 - 14:48

You ask one guard what the other guard would say, then go through the OTHER door.

I thought EVERYONE knew that... ph34r.gif


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#6 Mushroom

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Posted 19 July 2006 - 16:32

You're quite close Bobifier, think about what you just said.
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#7 bobifier

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Posted 19 July 2006 - 16:35

QUOTE(Mushroom @ Jul 19 2006, 05:32 PM) View Post

You're quite close Bobifier, think about what you just said.

Well you turn it into a yes/no question, such as 'Oy, you, would that bloke over theyer tell me to go in this door' and then go through the door opposite to the one implied.

Actually, I once heard another answer to that one, and I can't remember what it was...
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#8 Mushroom

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Posted 19 July 2006 - 16:38

Well, since you're so close, I'll tell you, you ask 'Will the other guard tell me this door leads to freedom.' if the guard answers yes, then that is indeed the freedom door, and you go through. If the guard answers no, then the door leads to death, and you go through the other door. tongue.gif
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#9 bobifier

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Posted 19 July 2006 - 16:41

QUOTE(Mushroom @ Jul 19 2006, 05:38 PM) View Post

Well, since you're so close, I'll tell you, you ask 'Will the other guard tell me this door leads to freedom.' if the guard answers yes, then that is indeed the freedom door, and you go through. If the guard answers no, then the door leads to death, and you go through the other door. tongue.gif

That's wrong, in fact. If you were to ask the lying guard 'will blokey over theyer tell me that thissy here door will lead to freedom', he will inevitably say 'no'. Your algorithm would then send you through the door of doom.(Please excuse me writing in accents ph34r.gif )

And, I think you will find, my way works perfectly well.
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#10 Mushroom

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Posted 19 July 2006 - 17:02

No, I made a mistake, if the guard says no when you ask the question, then it is the freedom door.

If you ask the guard that lies if 'Blokey' will say this is the freedom door, and he says No, that means it is the freedom door because the other Guard would say it was the freedom door, so the lying guard says he wouldn't.


If you ask the truthful guard if the other guard would say this is the freedom door, and it is, the guard will say no as the other guard would say it is not the freedom door, and so he would tell you that.

O.K then another puzzle.

There is going to be a truel, which is a Duel involving three people.

The three participants:

Jim: A fantastic shooter who always hits the target.
Dave: A reasonable shooter who hits half the time.
Bob: A rubbish shooter who only hits a third of the time.

They are going to take turns shooting in the following order:

Bob,
Dave,
Jim.

Where should Bob shoot first?
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#11 superpyroman

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Posted 19 July 2006 - 18:30

behind him to make sure that he doesn't hit either of the other two, next dave will shoot jim as he is a better aim rather than bob as he doesn't hold a grudge against him for shooting him, if he hits then bob will have a 1 in 3 chance of winning and if he misses then he will still have the same odds whereas if he shot either of the others, chances are that he would get killed

that wasn't anywhere near impossible.....
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#12 bobifier

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Posted 19 July 2006 - 18:32

QUOTE(Mushroom @ Jul 19 2006, 06:02 PM) View Post

No, I made a mistake, if the guard says no when you ask the question, then it is the freedom door.

If you ask the guard that lies if 'Blokey' will say this is the freedom door, and he says No, that means it is the freedom door because the other Guard would say it was the freedom door, so the lying guard says he wouldn't.


If you ask the truthful guard if the other guard would say this is the freedom door, and it is, the guard will say no as the other guard would say it is not the freedom door, and so he would tell you that.

I'm sorry, I didn't absorb any of that, it can get quite confusing and I can't be bothered to concentrate tonight.

EDIT: And I agree with my brother's answer to the latest installment
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#13 superpyroman

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Posted 19 July 2006 - 18:42

QUOTE(Mushroom @ Jul 19 2006, 05:38 PM) View Post

Well, since you're so close, I'll tell you, you ask 'Will the other guard tell me this door leads to freedom.' if the guard answers yes, then that is indeed the freedom door, and you go through. If the guard answers no, then the door leads to death, and you go through the other door. tongue.gif



any answer that gives any kind of double negative would work. I can't think of many that haven't been said though

QUOTE(superpyroman @ Jul 19 2006, 07:30 PM) View Post

behind him to make sure that he doesn't hit either of the other two, next dave will shoot jim as he is a better aim rather than bob as he doesn't hold a grudge against him for shooting him, if he hits then bob will have a 1 in 3 chance of winning and if he misses then he will still have the same odds whereas if he shot either of the others, chances are that he would get killed

that wasn't anywhere near impossible.....



in fact I think a table could be drawn from this

assuming that each participant will always attack someone who has missed them or if none exists, the most threatening person.......

*starts drawing table*
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#14 superpyroman

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Posted 19 July 2006 - 19:10

IPB Image

here it is


I have declined to put any calculation on it yet and I'm not completely sure about the middle column, but it conveys clearly that my suggestion is best?
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#15 lizbun

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Posted 21 July 2006 - 14:56

You can ask "Is 1+1,2?" (question at the top)
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