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.)
(In reply to
That cannot be. by Brainteaser)
That may have been the case in the way it was told to you, but here it specifically states, "sometime next week."
The idea behind the answer here is that the students cannot be sure of the professors honesty. In fact, by logic, it is impossible for him to have told the truth (that doesn't mean he lied).
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Posted by Tristan
on 2003-11-12 19:20:34 |