Knights and Knaves: Judy, Rupert, Olivia, and Grace

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knights knaves

On an island, every inhabitant is either a knight, who always tells the truth, or a knave, who always lies. You meet Judy, Rupert, Olivia, and Grace. Judy says: "If Grace is a knave, then Olivia is a knight." Rupert says: "Olivia is a knight." Olivia says: "Rupert is a knave or I am a knight." Grace says: "Rupert is a knave and I am a knight." Who is a knight and who is a knave?

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Solution

Commit an attempt to unseal the proof. Write your answer — right or wrong, thinking it through is the point.

Once you've worked out who is who: how many of the 4 inhabitants are knaves? Answer with the number.

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