Question: The population of an island consists of two and only two types of people : the knights, who invariably tell the truth and the knaves who always lie. Suppose that the stranger asked X, instead, "How many knights among you?" Again X replies indistinctly. So the stranger asks Y, "What did X say?" Y replies, "X said that there is one knight among us." Then Z says, "Don't believe Y, he is lying!" Now what are Y and Z?
Answer:
Again the statement made by Y is false - "X said that there is one knight among us". Analyse these statement with 4 possible cases as above. In all the cases statement made by Y is false. Hence, Y is Knave and Z is Knight.