Sunday, April 22, 2007

You are lost in a forest. The forest is between two villages, A and B. People from village A always tell lies; people from village B always tell the truth. You want to go to village B.Then you see a man from either A or B. You can ask him only one question.Which question will you ask him to know for sure where village B is?

12 Comments:

Anonymous Anonymous said...

I will ask "Do you think B lies?".

If the person is from A, the answer will be Yes;
If the person is from B, the answer is No.

April 22, 2007 at 2:10 PM  
Blogger steven said...

But how do you know which path to take?

April 23, 2007 at 4:51 AM  
Anonymous Anonymous said...

"Do you think B lies over there?" and point in the direction of one of the villages.

If the person is from A, the answer will be Yes;
If the person is from B, the answer is No.

April 24, 2007 at 1:40 AM  
Blogger steven said...

OK, I should clarify - you don't know whether he is from village A or B.

April 26, 2007 at 2:53 AM  
Blogger steven said...

'If I were to ask an inhabitant of the other village, in what direction would she say that B lies?'

If the villager comes from B, they will tell the truth and point in the direction of A - as a villager from A would lie to you.

If the villager comes from A, they would lie and also point in the direction of A - as a villager from B would tell the truth.

So you go in the -other- direction to the one the villager points towards.

April 29, 2007 at 7:55 AM  
Blogger Jonathan said...

I recently discussed a new variation of the solution with a friend.

"If I were to ask you which direction to go to get to B, which way would you say?"

If he's from A, he will tell you the truth.
If he's from B, he will lie about his own lie and tell you the truth.

April 30, 2007 at 9:04 PM  
Blogger steven said...

I like that answer.

May 1, 2007 at 2:50 AM  
Blogger Vineet said...

Hi,
I would ask him "Where is your village?"
If the guy is from village A, he would show me the path to Village B.
If the guy is from Village B, then again, he would show me the way to village B.
Thus, I would always land up with the path to village B!

May 11, 2007 at 6:15 PM  
Anonymous Anonymous said...

Point to one direction, either A or B, and ask "Are you from that village?". That direction leads to A if the answer is "NO", or B if "YES".

July 7, 2008 at 5:22 PM  
Anonymous Anonymous said...

i would ask him where is your village because if he is from village A he will take you to village B because he lies and if he is from village B he will tell the truth and take you to village B because he never lies

September 16, 2014 at 2:22 AM  
Anonymous Anonymous said...

i would ask him where is your village because if he is from village A he will take you to village B because he lies and if he is from village B he will tell the truth and take you to village B because he never lies

September 16, 2014 at 2:22 AM  
Blogger RAJ BAJYA said...

I will ask him, That is your village?, pointing to village B.
If he is a truth speaker , he will say YES.
If he is a liar he will also say YES because he will lie about his village.
And If you point to Village A, both of their answer will be no.
So basically If you ask ,"that is your village ?" , they will always point to village B.

July 19, 2016 at 7:16 AM  

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