Brain Teasers
Truth or Lies
You are traveling down a path and come to a fork in the road. A sign lays fallen at the path indicating that one path leads to a village where everyone tells the truth and the other to a village where everyone tells lies. The sign has been knocked down so you do not know which path leads to which village. Then someone from one of the villages (you don't know which one) comes down the path from which you came. You may ask him one question to determine which path goes to which village. What question do you ask?
Answer
You point to either path and say, "Are you from this village?" If the person answers 'yes' then you are pointing to the truthful village, if they answer 'no' then you are pointing to the lying village.1)If you point to the truthful village what will a truthful person say in answer to your question?
2)If you point to the truthful village what will a untruthful person say in answer to your question?
3)If you point to the untruthful village what will a truthful person say in answer to your question?
4)If you point to the untruthful village what will a untruthful person say in answer to your question?
The answers to these questions are: 1. "yes", 2. "yes", 3. "no", 4. "no".
Note that in the two cases where the answer is "yes" you are pointing to the truthful village and in the two cases where the answer is "no" you are pointing to the untruthful village. Thus you can tell from the reply to which village you are pointing. You do not have to know to whom you are speaking.
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Comments
WOULDN'T IT BE EASYER TO ASK HIM DO PEOPLE
BOTH VILLAGES TELL THE TRUTH? YOU WOULD KNOW
RIGHT AWAY WITH ONLY 1 QUESTION.
BOTH VILLAGES TELL THE TRUTH? YOU WOULD KNOW
RIGHT AWAY WITH ONLY 1 QUESTION.
I agree
But OD-1, if I´m not mistaken, you wouldn´t know the answer right away with your question. You would have to wait to see the path the person would take to know the answer exactly. Remember, the man is coming from the same path which you came and not from one of the villages. Besides, there is also the possibility that he is from one village and takes the path to the other village just to visit one of his friends or relatives there. In this case, Lester´s question is more sure.
And how do you know the untruthful person is lying? Just because you said they are untruthful doesn't mean they always tell a lie.
You don't have to wait for the person to go back.
If you see the answer you will realise that in case if the village is the truthful one you will get a 'yes' as the answer from both the truthful and untruthful persons whereas you would get a 'no' from both the persons if the village is untruthful.
Hence we do not have to wait till the person goes back.
From their answers you can know that which village is which.
If you see the answer you will realise that in case if the village is the truthful one you will get a 'yes' as the answer from both the truthful and untruthful persons whereas you would get a 'no' from both the persons if the village is untruthful.
Hence we do not have to wait till the person goes back.
From their answers you can know that which village is which.
The answer is incorrect. You will not get the answer with only one question. I thought a long time on this teaser, and at first gave the answer that is posted, but then found it incorrect. Since When you'll point to a village, i.e. the lying village, and the person whom you speak to happens to be from the truth telling village, then he will say "no" to the posted question, and if he is the lyer then he will say "yes" and vice versa, so you cannont possibly know which village is which with one question. You'll need a minimum of two questions. First to find out if the person is a truth-telling or lyer, and you can do that only if you ask a question to which you know the answer.
how can a lyer say 'yes' to his own village ie, the lying village. Hence my above comment holds good and the answer is correct..
Okay, this is how it works! The answer is correct. When you point to the lying village, both a lying and an unlying person will say no! And when u point o the truthful village, both will say yes, because the truthful one will tell the truth and the other will lie, obviously. The answer is correct.
But couldn't you also just ask a simple question such as "Do you have legs?" The lying person will say no, but they obviously just walked over to you. Or ask what sex the person is, any simple question really.
Turd we're not trying to find whether the person is truthful or a lyer. If you see the question we have to find which village is which.
Okay. Why couldn't you ask them a question about something like habitual action? Like you could ask them if the sun rises in the east or the west. And we all know that the sun rises in the east. So if he came from the untruthful village he could lie about it. Then we would know where he came from. Does it make sense????
The person could be leaving the town he wasn't from.
How many times does this have to be said? THE SOLUTION IS 100% CORRECT! You are NOT trying to find out whether the person is truthfull or not, YOU ARE TRYING TO FIND WHICH VILLAGE HE IS FROM. If you know he's a liar that doesn't help because he could have been visiting friends or something. When asked "Is that your village?" a truthfull person will answer yes if you point to the truthfull village and no if you point to the untruthfull village. A liar would also say yes if you pointed to the truthfull village and no if you pointed to the untruthfull village, because hes a liar. So whichever village they point to is the truthfull village. OK?
Yikes. Scary how many people don't get this...
Good 1! Tricky though.
Why can't you say "are you lying?
I think the best would be "Are you a person?"
I came up with a different answer based on the same principle. The teaser doesn't specify that it has to be a yes/no question you ask, so, I ask: "Which village is yours?"
The liar will point me away from the lying village.
The truthteller will point me to the truthtelling villages.
So regardless of whether the man is telling the truth or lying, I will be pointed to the truthful village.
The liar will point me away from the lying village.
The truthteller will point me to the truthtelling villages.
So regardless of whether the man is telling the truth or lying, I will be pointed to the truthful village.
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