Lying about truth

  • Thread starter vikasj007
  • Start date
  • #1
vikasj007
162
1
I suppose this one should not be very difficult for all you smart people out there, but anyways, let's see.

This is about two brothers who together, run a phone booth at an intersection of two highways, one going to city A and the other going to city B. It is known about the brothers that the elder one always speaks the truth while the younger one always lies about anything you might ask him.

A man going to City A came upto that intersection and now is not sure which of the two ways to take. He is aware of the strange habit of the brothers at the phone booth, and sees that one of them is at the booth. His problem is that he does know which of the brothers is at the shop at that moment.

In order to ask about his way, he can just ask one question to that man. Find out which is that one question that he should ask so that he is certian to go the correct way.

and remember, he can ask only one question.
 

Answers and Replies

  • #2
Andre
4,509
74
If I asked your brother if this is the road to city A, what would he answer?
 
  • #3
Matrixman13
32
0
If you ask him if he has a brother, then you can tell who it is. The person who always lies will have to say no. The person who doesn't will say yes.
 
  • #4
Njorl
Science Advisor
285
17
You ask, while imitating Sam Jackson, "Which way to City A. If you're lying to me, I'm going to come back and kick you're ass. I don't give a damn about no logic puzzles! What kinda jackass brothers always lie while the other tells the truth! DON'T ANSWER THAT! It was rhetorical. Don't they teach you rhetoric in logic puzzle land, you lamea** m***** f*****!"

Njorl
 
  • #5
Gokul43201
Staff Emeritus
Science Advisor
Gold Member
7,176
21
(-1)*(1) = (1)*(-1) = -1
 
  • #6
Andre
4,509
74
Again
If I asked your brother if this is the road to city A, what would he answer?

suppose it is true, the road is going to city A. If the other brother whom I would have asked, was the lying one, he would have said "no" and the brother speaking the thruth to me would tell me that honestly: "He would have said: No"

Now, if the other brother was the honest one, he would have answered "yes", so the lying brother would invert that and say "No" as well

So in both cases: No, this is indeed the road to city A
And likewise the other case: Yes, this is not the road to city A.
 
  • #7
DrKareem
101
1
You'd ask the gentleman: "If i asked your brother about the way to city A, which road he'd give me?" and then go to the other road.
 
  • #8
vikasj007
162
1
andre here has given the correct answer with the correct explanation.
GREAT WORK!
i hope next time i can come up with something bit more difficult so that it takes a bit more of your time and thought.
Bye
 

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