Hello 911....

Here’s another fun liar/truthteller type logic problem, almost verbatim from Tanya Khovanova** who doesn’t know its origin:

“Folks living in Trueton always tell the truth. Those living in Lieberg always lie. People living in Alterborough alternate strictly between telling the truth and lying. One night 911 receives a call. The caller says, ’There’s a fire here, help!’ The operator cannot identify the phone number, so she asks, ‘Where are you calling from?’ The caller replies, ‘Lieberg.’ Assuming no one has overnight guests from another town, where should the firemen go?”

** -- in Volume 3 of “The Mathematics of Various Entertaining Subjects” due out shortly

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answer:  ONLY an alternator could say they're from Lieberg; a truthteller (who always tells the truth) would be lying to claim such, and a liar (who must live there but lie about it) would be telling the truth. The alternator's second statement (that they are in Lieberg) must be a lie, and so their first statement must be true, meaning there is a fire and it is in Alterborough.