To Introduce the Idea of Paradox from Martin Gardner's New Mathematical Diversions From Scientific American




(1) On a piece of paper write the phrase,

Sometime before the end of this class period, you will write the word "NO" on a note card which I have given you.

(2) Fold the paper and put it in an envelope. Give this to a student.

(3) Now give that student a blank note card and explain that you have just written a prediction about an event which will definitely happen or not happen during this period.

(4) Request that he write "YES" on the card if he guesses it will happen or "NO" on the card if he guesses it will not happen.

(5) Ask him to fold the card and give it to another student for safekeeping.

(6) Now ham it up - 50-50 chance; I'll give 10 to 1 odds that he is wrong. Offer NO HOMEWORK if he is right.

(7) Then get the response card from the student and read the prediction aloud.



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