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A surprise exam (Posted on 2002-04-26) Difficulty: 3 of 5
A professor tells his class that he will give them a surprise examination sometime next week.

For our purposes, an examination is considered a "surprise" if on that day, the class is not 100% sure that they will get an examination. (If they only suspect it, the examination can still be a surprise.)

Having given the class this warning, is it still possible for the professor to give them a surprise examination next week? (Assume that he will not give them an exam if it will not be a surprise.)

See The Solution Submitted by levik    
Rating: 3.3684 (19 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re(2): You guys are forgetting something... | Comment 22 of 39 |
(In reply to re: You guys are forgetting something... by SilverKnight)

First of all, to address your issue of "What if he did it on Monday", he lied then. The Assuming we are given to do and the problem are in contradiction.

I understand what you are saying. We can't eliminate Friday if TODAY is Wednesday Evening because there is still Thursday and Friday, and we don't know what day.

If it was Wednesday Evening, the students could think "The test must be tommorrow if the professor isn't lying. If he doesn't give it tommorrow, there is no way he could give it without lying, so he can't give it tommorrow."

Does this make sense, and did I interpret what you said properly? I am hoping to address your problem more closely instead of just repeating what has been said by others.

  Posted by Gamer on 2003-10-01 20:17:07

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