I was reading the magician's post on game theory and it made me remember a riddle I heard a long time ago. Kudos if you can get the right answer



So your walking down a path in a forest and you get lost. It's getting really late and you come to a split in the road, one heading left and one heading right. One of these paths lead to death and the other path leads back home. There is a house right before the split and twin sisters live in the house. One sister always tells the truth and one sister always lies. You cannot turn back in the path, so you have to choose one direction to go. You knock on the door and a sister comes out. You may only ask one question but you don't know which sister comes out. What do you ask?

 

Whoa... my question would be...

Is this the sister that lies?

 

How would that tell you which way to get home?

 

just tell whichever sister answers the door that her other sister ran down such-n-such a path and you're really worried about her.

if the sister runs down that path, you know it's safe, so follow her.

if the sister doesn't, she knows her sibling is dead. comfort her, have her walk down the other path with you and try to console her at your pad. a lil red wine, some time to reminisce on their childhood together... (and it doesn't matter if she lies or not, you're just trying to get lucky)



ok, that's my smartass answer. I'll give ya a Dark Logic answer in a bit. (first I need to reply to AIT1 )

 

You pick either side and say,"Would your sister tell me this is the path to death?"

If it were the path to death the truth sister would say no because the liar sister would not reveal this fact. The liar would also say no because here sister would say yes and hence she has to lie so you take the opposite path.

If it were the path to home the truth sister would say yes because here sister would lie and the liar sister would say yes because she's have to lie about her sister's answer so....

no=death and yes=home in this question. It would be the opposite if you asked does this path lead home.

 

s2000raj! v nice!

 

[QUOTE]Originally posted by s2000raj
You pick either side and say,"Would your sister tell me this is the path to death?"

If it were the path to death the truth sister would say no because the liar sister would not reveal this fact.

 

The "classic" answer is:

"If I asked you yesterday which path is safe, what would you have said?"

Clearly the sister who tells the truth will tell you the correct path; less obvious is that the lying sister will, too.

Yesterday she would have lied. Today she will lie about yesterday's answer, inadvertantly telling the truth.

 

I think you guys are overlooking the wealth of opportunity by having two sisters willing to chat with you who live just up the road!