A teacher announces in class that an examination will be held on some day during the following week, and moreover that the examination will be a surprise. The students argue that a surprise exam cannot occur. For suppose the exam were on the last day of the week. Then on the previous night, the students would be able to predict that the exam would occur on the following day, and the exam would not be a surprise. So it is impossible for a surprise exam to occur on the last day. But then a surprise exam cannot occur on the penultimate day, either, for in that case the students, knowing that the last day is an impossible day for a surprise exam, would be able to predict on the night before the exam that the exam would occur on the following day. Similarly, the students argue that a surprise exam cannot occur on any other day of the week either. Confident in this conclusion, they are of course totally surprised when the exam occurs (on Wednesday, say). The announcement is vindicated after all. Where did the students' reasoning go wrong?
4 Comments:
Eh u want your physics notes back?
8:37 PM
Bingo..this is what I'm doing now for my gem. Note... his reasoning is wrong because he is doing his proving backwards.
2:18 PM
Reason and persuasion hahaha
8:45 PM
hmm.. weird
"would be able to predict on the night before the exam that the exam would occur on the following day."
i thot it means tt if they are expecting on sunday tt it'll be on monday, and it doesn't happen on monday, they'll go "ok then monday's out, tuesday then" and prepare for tuesday and not bother about the original assumption. Therefore on day x they'll expect it to be on day x+1 so they'll never be surprised, no?
Or do they mean that because friday's confirm not the day, they happily think they are gepers and is able to 'feel' when the exam is on the night b4?
i mean, wat the heck were they thinking on tuesday nite?? having sex??
selwyn & edchong can explain further? thankx
11:02 PM
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