a, b, c, d are suspects in a case of corruption. It is now known that:
(i) At least one of the three persons other than d is guilty.
(ii) If d is guilty, then either b or c is not guilty.
(iii) If b or c is guilty, then so is a.
(iv) If two or more people are guilty, then d is one of them.
Questions: Who is definitely guilty? If either both b and c are guilty or neither of them are guilty, what conclusion can be drawn?
Four staff members (White, Gray, Brown, Black) attended a training course on identifying counterfeit bank notes. The instructor asked them to inspect three one-thousand-dollar notes.
Mr. White said, "The first note is genuine. The third one is counterfeit."
Mr. Gray said, "Both the second and the third notes are counterfeit."
Mr. Brown said, "The first note is geunine. The remaining notes contain one counterfeit one and one genuine one."
The instructor was very annoyed, and said, "The answer of everyone is half correct and half wrong! The success rate is the same as random guessing!"
Mr. Black sat in repose with his eyes closed. He has not looked at any of the three bank notes. (But he has studied logic in college with the greatest attention.) He gave all the correct answers without opening his eyes. Can you do the same?
There are three boxes, A, B & C, only one of which contains a treasure. On each of them is engraved a statement. These boxes are made either by Freyr or by Loki. Boxes made by Freyr always have true statements engraved on them, whereas boxes made by Loki always have false statements engraved. The statements on the three boxes are as follows:
A: "The treasure is in Box B."
B: "Exactly one of these boxes is made by Loki."
C: "None of these boxes is made by Freyr."
Questions: Which box contains the treasure? Which box(es) is/are made by Freyr and which by Loki?
[ 本文被Chelsea在2012-01-09 21:11重新編輯 ]