A: I am older than B B: I am older than A and C C: I am older than A and B One among A,B and C is telling a lie. The other two are telling the truth. Who is telling lie?

Testing each possibility shows only one is consistent: if B is lying, then A's claim (A>B) and C's claim (C>A and C>B) can both be true simultaneously, giving the order C>A>B with no contradiction. If A were lying instead, B's and C's claims would both have to be true, but B claims to be older than C while C claims to be older than B — a direct contradiction, so A can't be the sole liar; the same kind of contradiction rules out C being the liar.

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