Question 195237: A teacher entered a room and saw four students- Andrea, Beth, Carlos, and Don. On the teacher's desk was an apple. The teacher asked each student who brought it. Andrea said,"I didn't bring it." Don said," Beth brought it." Beth said,"Carlos brought it." Carlos said," Beth didn't tell the truth when she said i brought it."
Answer by solver91311(24713)   (Show Source):
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Presuming that everyone but Beth was telling the truth, including Don, Beth brought the apple. Also, by elimination, if Carlos told the truth, then not only was he saying that Beth was untruthful, he said he didn't bring the apple. Don also indirectly said that he didn't bring it, and Andrea said she didn't bring it. The only one left is Beth.
Update
The student informed me that she left off an important detail. Only one of the statements is actually true. This changes things significantly:
If Carlos is untruthful, then Beth must be truthful and Carlos brought the apple, BUT if Beth is truthful, then every other statement is untrue and Andrea's statement that she did not bring the apple is untrue meaning Andrea brought the apple. This contradicts the idea that only one student brought the apple.
Therefore Carlos must be truthful, meaning everyone else is untruthful. This takes us back to Andrea who, untruthfully, said she didn't bring the apple. Therefore she actually did.
John
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