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Aprinceto.3003 net.math utcsrgv!utzoo!decvax!ucbvax!ihnss!eagle!mhtsa!allegra!princeto!stat Tue Mar 16 15:42:55 1982 Paradox I have spent many hours discussing this paradox and have heard dozens of attempts at resolving it and have never quite been satisfied.

Mr. Smith tells his class that he will give them a surprise test sometime in April. He explains that by 'surprise' he means that they will not know when they arrive in class on the day of the test whether they will be writing the test that day. Alec Smart reasons that the test will not be on the 30th, for it would then not be a surprise. 'Thus', he continues, 'on the 29th, since I know it won't be on the 30th, he has to give it that day if he hasn't already, so it can't be on the 29th.' Arguing inductively he comes to the conclusion that the test cannot be given as a surprise on any day in April, he doesn't study, and is quite suprised when Mr. Smith gives a surprise test on the 17th of April. Why was Alec surprised?

Please respond to me at ...ihnss!mhtsa!allegra!princeton!stat.

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