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Erasing digits (Posted on 2002-04-27) Difficulty: 3 of 5
Digits from 1 to 9 are written on the board.

A student erases a few of them, and instead writes the digit(s) of their product. (For example if he erases 4, 3 and 7 he would write the digits 8 and 4 since 4 * 3 * 7 = 84.) He also writes a few other random digits on the board.

He repeats this process until only one digit remains on the board. What is this digit and why?

See The Solution Submitted by levik    
Rating: 2.9091 (11 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: i have to disagree | Comment 5 of 10 |
(In reply to i have to disagree by Cory Taylor)

I agree with the idea of the process being infinite, but I also agree that a student cannot be 100% random. I also believe that the student will start add zeroes "randomly" as the review the results.
  Posted by cges on 2002-12-11 06:24:21

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