In an Island the natives lie and visitors speak truth. A man wants to know whether a salesman beside him in a bar is a native or a visitor.
He asked him to ask a woman beside him whether she is a native or visitor. He replied, “She says she is a visitor.” Then he was immediately able to determine if the salesman is a native or a visitor. Is the salesman a native or a visitor?
Answer
The salesman is a visitor and he is telling the truth.
If the woman is a visitor, and asked if she is a visitor, she will answer truthfully: “Yes”.
If the woman is a native, and asked if she is a visitor, she will answer falsely: “Yes”.
In either case, the woman will answer, “Yes.” Since the salesman did not lie, he has to be a visitor.