Brain Teaser #6

[FJRottie]

I'll give you an old one, that actually has an answer.

You are walking down a road.

There is a fork ("Y" junction) in the road.

One of the roads leads home.

The other road to death.

You are not allowed to turn around and go back where you came.

At the fork in the road is a house, where two identical brothers live.

The brothers are absolutely identical looking and wear identical clothes.

The only difference is that one will always lie, and the other will always tell the truth.

You don't know which road is which, but the twins do.

One of the twins is standing outside, at the fork in the road.

You are allowed to ask the twin one question.

Find out which is the road home with your question.

What is your question ?

 

[yanktar]

"If I were to ask you if this was the correct road to <whereever>, would you say 'Yes'?"

The dishonest twin is forced to answer truthfully. The honest twin answers truthfully.

 

[FJRottie]

The dishonest twin is forced to answer truthfully.

He is going to lie....always.

You don't know which road you are asking about. So is he giving you the right answer....no.

Don't think too deep.

 

[yanktar]

Take another look. He's forced into a double negative. If you ask "is this the road to...?" he lies. But you are asking him "would you say 'yes'" He lies about what he would lie about--leaving you with the truth.

The assumption is that the liar is consistent, and ALWAYS lies, as opposed to saying what will deceive.

How's this as an alternative?:

"Do you realize that I'm holding this 9mm Glock to your head, and it's loaded, and I'm dragging your sorry ass down the road with me, and if it's the wrong road I'm gonna shoot you so it hurts more than you can imagine and it takes a really, really, REALLY long time for you die, screaming all the way?"

 

[twowheelnut]

Dammit! I gotta agree with YT, AGAIN! Oh, the humanity!

 

[FJRottie]

Ok, he is a liar and a deceiver. Anyway, he will lie. He is uncapable of telling you the truth.

If you asked him your question pointing to the wrong road, he will say yes.

If you asked him your question pointing to the right road, he will say no.

But that is the liars answer.

The honest twins answer is the opposite.

But you don't know which twin it is or which road is which.

A double negative is the use of two or more negative words in the same sentence to produce a strong emphasis on the positive or negative meaning in the verb.

i.e.

Would you not object to not having a beer ?

We don't need no education.

We don't need no thought control.

Your double positive will not resolve to a negative.

Don't think too deep.

 

[slapnpop]

The answer is "which road would your brother say is the road home?" and the answer will always be the wrong road. This way a lie is forced into the answer, and there's no possibility for a second lie.

 

[FJRottie]

We have a winner.

Ok funs over.

 

[twowheelnut]

The answer is "which road would your brother say is the road home?" and the answer will always be the wrong road.  This way a lie is forced into the answer, and there's no possibility for a second lie.

Not necessarily. What if you asked the question of the lying brother and he replied, "What? I don't have a brother. Now, get off my lawn or I'll bust a round of salt rock up your ass!"

 

[yanktar]

Ok, he is a liar and a deceiver. Anyway, he will lie. He is uncapable of telling you the truth.If you asked him your question pointing to the wrong road, he will say yes.

If you asked him your question pointing to the right road, he will say no.

But that is the liars answer.

The honest twins answer is the opposite.

But you don't know which twin it is or which road is which.

A double negative is the use of two or more negative words in the same sentence to produce a strong emphasis on the positive or negative meaning in the verb.

i.e.

Would you not object to not having a beer ?

We don't need no education.

We don't need no thought control.

Your double positive will not resolve to a negative.

Don't think too deep.

Sorry if my logic escapes you. It's unassailable. Take ANOTHER look. It's a simple case of nested binary logic, but put in the form of a sentence.

The liar lies about what he would say. But what he would say would be a lie. So by lying about the lie, he's forced into truth.

Assume Road A is the Road to Death.

"Is this the road to Death?" The liar says "No".

"If I asked you if this is the road to Death, would you say 'Yes'?" The liar would say "No" to the inner question. But to say "No" to the outer question means he would be telling the truth about what he would say about the inner question.

But he cannot tell the truth about that--he must lie. So what he would say is a lie "No" to the direct question, and what he tells you he would say is a lie "Yes", which of course has tricked him into telling you the truth.

I didn't strain at all--the logic is impeccable.

 

[FJRottie]

:lol: :lol:

Whatever you wanna call your thinking, it will not work.

Have a nice day.

Someone delete this thread.

 

[donaldb]

When are you people gonna learn that YT is always right!, I mean left, uh I mean right--oh never mind :lol:

 

[Rogue]

When are you people gonna learn that YT is always right!, I mean left, uh I mean right--oh never mind :lol:

:rolf:

 

[grnarrowe]

Dammit!  I gotta agree with YT, AGAIN!  Oh, the humanity!

You beeter seek treatment RIGHT AWAY!! :haha:

I have a headache after reading YT's answer, pass the Burbon please.

 

[azbikergirl]

I didn't strain at all--the logic is impeccable.

Yup. 'Fraid so.

 

[yanktar]

Dammit!  I gotta agree with YT, AGAIN!  Oh, the humanity!

You beeter seek treatment RIGHT AWAY!! :haha:

I have a headache after reading YT's answer, pass the Burbon please.

Must be a migraine---What's burbon?

Me, I like old rum...

 

[grnarrowe]

Dammit!  I gotta agree with YT, AGAIN!  Oh, the humanity!

You beeter seek treatment RIGHT AWAY!! :haha:

I have a headache after reading YT's answer, pass the Burbon please.

Must be a migraine---What's burbon?

Me, I like old rum...

Sorry, can't spell. Pass the Baliey's.

 

[yanktar]

Dammit!  I gotta agree with YT, AGAIN!  Oh, the humanity!

You beeter seek treatment RIGHT AWAY!! :haha:

I have a headache after reading YT's answer, pass the Burbon please.

Must be a migraine---What's burbon?

Me, I like old rum...

Sorry, can't spell. Pass the Baliey's.

LOL!

Ok, ok, I'd rather have burbon or bourbon than Bailey's (or Baliey's).

But I like Rhum or Rum better!

(I cheated..."Rhum" is what the french-speaking islands call rum).