Suppose that you meet three people, Anita, Boris, and Carmen. What are Anila, Boris, and Carmen if Anila says "I am a knave and Boris is a knight" and Boris says "Exactly one of the three of us is a knight"?
Solution:
Step 1:
In this problem we need to determine what exactly they are.
Given: Anita says “I am a knave and Boris is a knight” and Boris says “Exactly one of the three of us is a knight”.
We know that knight always tell the truth and knave always tell the lie.
Let us assume that, Anita says “I am a knave and Boris is a knight” is true.
So, Anita is a knave.But we know that knave always tell the lie.So, the second statement Boris is a knight is false.
Hence, Boris must be a knave.
Therefore, Anita is a knave and Boris is a knave.