On an island each person either always tells the truth or always lies. Marcus says: "Isla is a liar." Isla says: "At least two of the three of us are liars." Kiran says: "Marcus and Isla are both liars." Which of the following is correct?
Answer and explanation
Correct answer: A. Truth-tellers: Isla; liars: Marcus and Kiran
- Step 1: Try each possible assignment of truth-teller or liar and check every statement against it. Step 2. Only one assignment makes all three people consistent, which is: Truth-tellers: Isla; liars: Marcus and Kiran. Answer: Truth-tellers: Isla; liars: Marcus and Kiran. Why not the others: 'Truth-tellers: Kiran; liars: Marcus and Isla' fails because Marcus would be a liar but the statement "Isla is a liar" would then be true; 'Truth-tellers: Marcus; liars: Isla and Kiran' fails because Isla would be a liar but the statement "at least two of the three of us are liars" would then be true; 'Truth-tellers: Marcus and Isla and Kiran; liars: nobody' fails because Marcus would be a truth-teller but the statement "Isla is a liar" would then be false.
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