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The lion, the unicorn and the day of the week

liarslogicdays-of-weekclassic

In the forest live a lion and a unicorn. The lion lies on Mondays, Tuesdays and Wednesdays and tells the truth on the other days. The unicorn lies on Thursdays, Fridays and Saturdays and tells the truth on the other days. On Sundays both tell the truth.

Alice meets them both. The lion says, "Yesterday I was lying." The unicorn says, "Yesterday I was lying."

What day of the week is it?

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For each creature, go through the seven days and check on which days its sentence is consistent with its behaviour that day. Remember that a liar's statement must be false.

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The theory behind this question.

Cheryl's Birthday and Iterated KnowledgeLogic and QuantifiersOne Question, Two Guards, One DoorProof Techniques: Direct, Contrapositive, ContradictionAdaptive Versus Pre-Committed Weighing Strategies

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