On an island, there are only 2 kinds of people, truthtellers, who always speak the truth and liars who always lie.
One day, on the island, C who is a truthteller meets 2 friends, A and B. C knows that one of A and B is a truthteller and the other is a liar.
C asked A, "Do you always speak the truth?"
A said something that C could not understand.
So C asked B, "What did A just say?"
B replied: "A said no."
So, who is the liar, A or B?
Difficulty rating:
Solution:
If B was a truthteller then it would mean that A must have said, “no”. That would mean that A was a liar. But, this would mean that A is telling the truth. This isn't possible. So, B is clearly lying. This means that B is the liar.