In a small village there are two kinds of people: liars and truthtellers.
Everybody knows everybody and everybody knows as well who is a liar and who’s a truth-teller.
I approach six villagers and pose the same question to each of them:
"How many liars are among you?"

I get six distinct answers (integers, of course) and deduce the true one.

How many liars are in that group?

Liars always lie and truthtellers never do.

(In reply to re(2): Summing up - spoiler by Ady TZIDON)

Just a few minutes ago the "official" solution was still in the solution queue, and only just now has become live.  While it was still in the queue it could have been edited, at least by a scholar; I don't know if by the poser. Keep this in mind for the future; if you have not made the solution public it can still be edited.

Posted by Charlie on 2015-11-17 10:57:38