Logic0909 - 1.19 (application of NGP) Three natives – a...

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Unformatted text preview: 1.19 (application of NGP) Three natives – a knight, a knave, and a spy (neither a knight or a knave) Ask two questions to find out who the spy is. Again there is no single yes/no question in this case like “are you a knight if and only if you are a spy”? Be careful that NGP doesn’t apply if the answerer is a spy! Still by the first question, you can find out Ask A: are you a knight if and only if B is a spy? If A is not a spy, NGP applies. L If the answer is yes, B is the spy and C is not the spy. L If the answer is no, C is the spy and B is not the spy. (because we have assumed that A is not a spy). If A is a spy, then B and C are not spies. Therefore, if the answer is yes, regardless of whether A is a spy or not, C is not the 1.20 (metapuzzle) Why is it called a “meta”puzzle? Missing information is provided by the fact that the questioner could solve it. A: both of us are knights....
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This note was uploaded on 02/04/2010 for the course HSS Hss105 taught by Professor Yeelee during the Fall '09 term at Korea Advanced Institute of Science and Technology.

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Logic0909 - 1.19 (application of NGP) Three natives – a...

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