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.)

It's sunday evening, assuming the prof is telling the truth, and IS giving a surprise test this week, are you 100% sure (ie willing to bet your life, money, pet goldfish etc) that he will give the test on Monday?
Surely not!
Monday evening - no? etc.
Only Thur evening do you KNOW it has to be on Friday - on Tue evening, it could still be on 3 days.

You can't rule out Thursday as a possible date until Wed evening.

(Alright, it's a paradox and unsolvable - but I like thinking of myself in bed the previous day wondering what will happen)

Posted by Dacre on 2003-10-23 11:03:59