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Tribe Travail (Posted on 2014-01-21) Difficulty: 3 of 5
On a certain island, there are three tribes - the Whites, the Oranges, and the Lemons which have different standards of veracity. It is not possible to distinguish them otherwise.
Whites are the knights who always tell the truth; Oranges are the liars who always speak falsely. Lemons are knaves who tell the truth and lie alternately, albeit not necessarily in this order.

A visitor was somewhat confused recently when he was introduced to three natives named Mr. White, Mr. Orange, and Mr. Lemon, who belong to the White tribe, the Orange tribe, and the Lemon tribe - albeit not necessarily in this order. There was also a fourth native named Mr.Yellow.

The visitor asked each of the first three natives (a) what his own tribe was, and (b) what was Mr. Yellow's tribe. To these questions, the responses of the three natives was as follows:

Mr. White replied: "I'm not a White. Mr. Yellow is an Orange."
Mr. Orange replied: "I'm not an Orange. Mr. Yellow is a Lemon."
Mr. Lemon replied: "I'm not a Lemon. Mr. Yellow is a White."

To which tribe does Mr. Yellow actually belong?

No Solution Yet Submitted by K Sengupta    
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Solution Too Much Information (spoiler) Comment 3 of 3 |
Actually, we do not need the information that Mr. White, Mr. Lemon, and Mr. Orange belong to three different tribes.

Further, we do not need statements from Mr. White or Mr. Orange.

The puzzle question can be answered by just considering Mr. Lemon's two statements: "I'm not a Lemon. Mr. Yellow is a White."

This statements cannot be made by an Orange (liar), because that would make the first statement true, so Mr. Lemon must be a White or a Lemon.

If he is a White (Knight), then both statements are true.
If he is an Orange (Knave), then the first statement is false, so the 2nd statement is true.
In either case, Mr. Yellow is a White.

  Posted by Steve Herman on 2014-01-21 23:28:11
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