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Liars, truth tellers and random answerers, revisited
Posted 07 December 2012 - 10:14 AM
You're driving from your home town to visit a friend in Elmdale. You reach a complex intersection where roads lead out in nine directions, evenly spaced, 40 degrees apart. Unfortunately, Hurricane Sandy has blown down the sign, with its nine arrows now pointing out at a random orientation. You have no other indication of which road is the one that leads to Elmdale.
Fortunately, perhaps, you meet five travelers at the intersection. One of them tells you that two of the group are truth tellers, two are liars and one answers truthfully or falsely, at random. Two others of the group confirm that statement, while the other two seem disinterested and offer no comment. After making it clear to them you are looking for the road that leads to Elmdale, one of the silent travelers tells you that the group is not from the area and in fact none of the five can tell you which road that is.
Suspecting that he is a liar, you start to ask the one that spoke first which road is the desired one, but the Original Poster interrupts you and says that you have used your allotment of questions.
Without guessing, how do you make the right choice, and meet your friend?
- Bertrand Russell
Posted 07 December 2012 - 03:12 PM
no clue on this one. seems to me you can at most eliminate two roads.
Posted 07 December 2012 - 10:30 PM
- Bertrand Russell
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