Knights and Knaves: Frank, Heidi, Grace, and Ivan
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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 Frank, Heidi, Grace, and Ivan.
Frank says: "Grace is a knave or Heidi is a knave."
Grace says: "Ivan is a knight or I am a knave."
Ivan says: "I am the same type as Heidi."
The others say nothing.
Who is a knight and who is a knave?
Hints
Hint 1
Hint 2
Hint 3
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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