Ếch hay cóc?
Trong một đầm lầy ma thuật, có hai loài lưỡng cư biết nói: cóc luôn luôn nói đúng và ếch luôn luôn nói sai.
Bốn loài lưỡng cư, Brian, Chris, LeRoy và Mike sống cùng nhau trong đầm lầy này và chúng đưa ra những tuyên bố sau:
Brian: “Mike và tôi là những loài khác nhau”.
Chris: “LeRoy là một con ếch”.
LeRoy: “Chris là một con ếch”.
Mike: “Trong bốn người chúng tôi, ít nhất hai người là cóc”.
Có bao nhiêu loài lưỡng cư là ếch?
Ếch hay cóc?
Trong một đầm lầy ma thuật, có hai loài lưỡng cư biết nói: cóc luôn luôn nói đúng và ếch luôn luôn nói sai.
Bốn loài lưỡng cư, Brian, Chris, LeRoy và Mike sống cùng nhau trong đầm lầy này và chúng đưa ra những tuyên bố sau:
Brian: “Mike và tôi là những loài khác nhau”.
Chris: “LeRoy là một con ếch”.
LeRoy: “Chris là một con ếch”.
Mike: “Trong bốn người chúng tôi, ít nhất hai người là cóc”.
Có bao nhiêu loài lưỡng cư là ếch?
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
Giả sử Brian là cóc (nói thật) $\Rightarrow$ Mike là ếch (nói dối).
$\Rightarrow$ Chỉ có Brian là cóc $\Rightarrow$ LeRoy và Chris là đều là ếch (nói dối).
Nhưng Chris nói LeRoy là ếch $\Rightarrow$ mâu thuẫn.
Vậy Brian nói dối (là Ếch) $\Rightarrow$ Brian và Mike cùng là loài ếch (nói dối).
$\Rightarrow$ Chỉ có 1 con cóc và 3 con còn lại là ếch (*).
Nếu Chris là Cóc (nói thật) $\Rightarrow$ LeRoy là ếch (nói dối) $\Rightarrow$ Thỏa mãn (*).
Nếu LeRoy là Cóc (nói thật) $\Rightarrow$ Chris là ếch (nói dối) $\Rightarrow$ Thỏa mãn (*).
Vậy có 3 loài lưỡng cư là ếch.
Đáp án: 3.
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