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        riddles >> hard >> Fork in the Road I
        
(Message started by: AutumnEffect on Aug 23rd, 2006, 3:48pm)
Title: Fork in the Road I
Post by AutumnEffect on Aug 23rd, 2006, 3:48pm
I'm sorry to bother you all, but, I'm having a hard time figuring out Fork In Road I.
Is there anyone that knows the answer and can tell me before I go crazy?

Thanks.

-AutumnEffect
Title: Re: Fork in the Road I
Post by Icarus on Aug 23rd, 2006, 5:58pm
You can find several answers in this thread (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1033971551;start=0). The one in the first post is the intended answer, though Chronos was right that it needs to be tightened up so that there are only two possible replies ("Which of these two villages do you come from?").

But you can gain some insight by reading the rest of the thread. James Fingas in particular has some very good points to make.
Title: Re: Fork in the Road I
Post by LaCiTy on Sep 21st, 2006, 5:47am
U just need some elementary Bool algebra. It will help you solve this kind of problems without even thinking.

Say a true assertion is valued +1 and a false one is valued -1.

One is always telling the truth which can me modelled by a multiplication by 1. The other one always lies, that  is turns a true assertion into a false one and a false one into a true one, provided there are only 2 modalities. Thus, it acts like a multiplication by -1.

You do not know what person you encounter that is you do not know if she will multiply by 1 or -1. As you want a certain statement, you have to find an invariant, that is something that yield the same result in both cases.

It is not difficult to see that -1x 1 always yields -1. Thus, you just have to combine the 2, that is ask a question that involve both types of person, which you can easily do by questions of the type : what would the other person answer if i were to ask him ...

... if i were to ask him where the village of the cannibals is.

You know for certain that the answer will be false (-1 x 1 = 1 x (-1)), thus the indicated village is the one you want to head to.
Title: Re: Fork in the Road I
Post by rmsgrey on Sep 21st, 2006, 6:23am

on 09/21/06 at 05:47:14, LaCiTy wrote:
U just need some elementary Bool algebra. It will help you solve this kind of problems without even thinking.

Say a true assertion is valued +1 and a false one is valued -1.

One is always telling the truth which can me modelled by a multiplication by 1. The other one always lies, that  is turns a true assertion into a false one and a false one into a true one, provided there are only 2 modalities. Thus, it acts like a multiplication by -1.

You do not know what person you encounter that is you do not know if she will multiply by 1 or -1. As you want a certain statement, you have to find an invariant, that is something that yield the same result in both cases.

It is not difficult to see that -1x 1 always yields -1. Thus, you just have to combine the 2, that is ask a question that involve both types of person, which you can easily do by questions of the type : what would the other person answer if i were to ask him ...

... if i were to ask him where the village of the cannibals is.

You know for certain that the answer will be false (-1 x 1 = 1 x (-1)), thus the indicated village is the one you want to head to.

That would be the intended answer to Fork in the Road II - but it runs into problems with people who don't never respect no double negatives.

Particularly if (as is often the case in such riddles) one of the parties is translating into another language, it would easy to mistake a deliberate itroduction of additional layers of reference for a purely syntactical elaboration.

If you had put more thought into answering this particular question, you might have discovered that there is a simpler solution in this case.
Title: Re: Fork in the Road I
Post by dustmicester1 on Oct 2nd, 2006, 7:11pm
the one i just heard and figured out was you come to the fork and a villager is there and one path goes to sudden death and the other goes to a sure way to live. the one village always tells the true the other always lies what question do you ask.... you point one way and say if i were to ask you if this way leads to the truth village would you say yes?  if its the guy from the truth village and it is the way to the truth village he would say yes and if its the lier he would say yes as well because if he says no then its the truth. i think thats right its hard for me to explain. someone can elaborate more on mine if they want
Title: Re: Fork in the Road I
Post by tedwindsor on Apr 29th, 2007, 9:53pm
Ask any one of them "If i asked him," him being the other guy, "which road leads to the city of safety, what would he say?"

and you go the opposite way, no matter which person you ask, then answer is going to be a lie.
Title: Re: Fork in the Road I
Post by tedwindsor on Apr 29th, 2007, 9:55pm
This is the same solution for Fork in the Road II
Title: Re: Fork in the Road I
Post by rmsgrey on Apr 30th, 2007, 7:08am

on 04/29/07 at 21:55:11, tedwindsor wrote:
This is the same solution for Fork in the Road II

There's a "better" solution for this version that doesn't work for the other variation.

See if you can figure out what the significant difference between the two variants is, and how it can be exploited to get a simpler question...
Title: Re: Fork in the Road I
Post by Aneon on Jun 26th, 2007, 2:08am
You ask any twin, "What would the other twin answer to the question: which road leads toward village A", and you take the opposite. Because if you ask the one who lies, he will lie about the answer of the second twin which tells the truth ---> he tells you the way to village B.
If you ask the one who tells the truth, he will actually repeat exactly what the lier would say ----> he tells you the way to village B.

So, it does not matter whom you ask they will always show you the way to village B, and since you want to go to village A, you take the opposite.  
Title: Re: Fork in the Road I
Post by rmsgrey on Jun 27th, 2007, 9:26am

on 06/26/07 at 02:08:16, Aneon wrote:
You ask any twin, "What would the other twin answer to the question: which road leads toward village A", and you take the opposite. Because if you ask the one who lies, he will lie about the answer of the second twin which tells the truth ---> he tells you the way to village B.
If you ask the one who tells the truth, he will actually repeat exactly what the lier would say ----> he tells you the way to village B.

So, it does not matter whom you ask they will always show you the way to village B, and since you want to go to village A, you take the opposite.  

As I said earlier, there's a "better" solution using a simpler question, that relies on a feature of this version of the riddle.
Title: Re: Fork in the Road I
Post by Grimbal on Jun 27th, 2007, 9:40am
If you want to take them by surprise and ask a very common question, ask any one:
[hide]Where do you come from?[/hide]
But it is probably safer to be more specific:
[hide]Which way leads to the city from where you come?[/hide]
Title: Re: Fork in the Road I
Post by srn347 on Aug 29th, 2007, 10:49am
Ask them to take you to their village. Either way, it'll be the village of truth and safety. Many other answers also.
Title: Re: Fork in the Road I
Post by DON_CORLEONE on Nov 25th, 2007, 5:31am
for FORK IN THE ROAD 1 there will be a simple solution to ask which road leads to your village.

Both 1 and 2 can be solved by asking any one of them that if i had asked u 1 minute before that which road leads to ----(desired destination) what would have been ur answer.
Title: Re: Fork in the Road I
Post by Grimbal on Mar 6th, 2008, 1:38pm
I meant that in the sense: "Where do you come from, from this way or that way?".  The guy would point at the one or the other road.  Both would point at the road to the city of safety.

(edit: typo)
Title: Re: Fork in the Road I
Post by tiber13 on Mar 6th, 2008, 1:39pm
if he was from the land of cannibals, he would eat you, or if he was alive, there must be no people , because the cannibals would of eaten each other, and the guy would of been the last person

never thought that
Title: Re: Fork in the Road I
Post by Grimbal on Mar 6th, 2008, 2:17pm
OK, fixed the mistake.

Now you confuse me.  The riddle asks "What question could you ask to find out which path leads to the city of safety?".   So, you arrive, you ask one of them "Do I have green eyes".  He says no.  Now, where do you go?
Title: Re: Fork in the Road I
Post by onlyme722 on Mar 6th, 2008, 4:56pm

on 03/06/08 at 14:17:47, Grimbal wrote:
OK, fixed the mistake.

Now you confuse me.  The riddle asks "What question could you ask to find out which path leads to the city of safety?".   So, you arrive, you ask one of them "Do I have green eyes".  He says no.  Now, where do you go?


You know what.  I just realized my mistake.  It'd been a day since I read the riddle, and I just now realized that neither of them are actually GUARDING a road (for some reason I had it in my head that they each were in charge of taking post at the entrance to each city.)  My mistake :D.  Well, oh well hahaha, all I did was make an ass of myself .  I apologize for wasting your time.

I don't know what is wrong with me, the answer was right in front of me and you already said it.  I humbly apologize for questioning you.  I would have to agree that it's as simple as asking "which road leads to your city?" :) I don't know why it didn't click.  I promise...I actually am pretty smart, though I haven't done much in the way of proving it hahaha.


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