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Fork in the road

You are walking down a road and arrive at a fork that splits the road into two separate paths. When you reach, you meet two identical twins, each standing at the edge of one of the two paths. You have heard that there is a bag with $1,000,000 at the end of one path and you are told that one of the two twins always tells the truth and the other always lies. There is no way you can get to the end of both roads before the sun goes down.

What ONE question can you ask (of only one twin) that would lead you to the money?

"if i'm looking for the money, which path would your twin tell me to go down?"

There are two possibilities: either you approach and ask the liar your question OR you approach and ask the truth-teller your question.

If you ask the liar “where would your twin tell me to find the money?”, he would obviously tell you to go down the wrong path (because his twin would tell you go down the correct path and the liar must always lie).

Otherwise, you would ask the truth-teller your question: “where would your twin tell me to find the money?” and the truth-teller will also give you the wrong answer because he must honestly say what his brother would answer.

Either way, whichever answer you get from either twin, you go down the opposite path.

Comments


Jango

Question doesn't say that either of the twins know where the money is.

  

Sean Moran

Well you can kind of give them mystical quantities and say one of them ALWAYS tells the truth no matter if he/she knows it & same with the other twin lying. Although the answer to the solution's question could still be "I don't know" in that case...


Mayank Verma

Can you not simply ask one twin whether the other twin is his brother or not and since we know they are twins and one of them always speaks a lie, We can infer which route to take depending on the answer.


Gene

Another solution: point to one fork and say to one of the twins, "If I asked you if this was the path to the money, would you say yes?" Say it was the right path. If you asked the truth-teller, he of course would say yes. If you asked the liar outright if it was the right path, he would say no. But to answer the given question, he would lie and say yes. The same reasoning applies if it was the wrong path. Both would answer "no."

  

Vishal barot

good question !


Vishal barot

Good quiz but easy


Tarun245

Probably a question that asks one twin about the other twin's answer.


Adrian Mulvey

Ask the twins which road you go down. If I take both of you along the same road with me?


Chuck Gruber

You ask one of the two, "which road would your brother tell me was the right road?". Then take the opposite road.


Rede Batcheller

The version of this I remember probably qualifies these days as politically incorrect, but here goes: A man is walking to a town. He comes to an unexpected fork int he road, and doesn't know which way to go. An Indian is sitting at the juncture and the man wants to ask the correct way, BUT. He knows there are two tribes in the area, and members of one tribe ALWAYS tell the truth and members of the other tribe NEVER tell the truth. What does the man ask the India in order to find out which fork he should take?

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Submitted by
Aakash
about 4 years ago
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Difficulty 6.0 ?

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