You have an ink stamp that is so amazingly precise that, when inked and pressed down on the plane, it makes every circle whose radius is an irrational number (centered at the center of the stamp) black.

Is it possible to use the stamp three times and make every point in the plane black?

If it is possible, where would you center the three stamps?

(In reply to re(4): Brian's solution by Larry Settle)

Firstly, woohoo - my link worked. Please hold your applause for something others have been doing for years...

Well I'm not sure on what you mean by "countable". if you mean "finite" then I'd have to disagree - would you not be saying that there are a finite number of rational numbers?

And from where do you get that the proportion of rational numbers within the continuum is zero?

Posted by Cory Taylor on 2003-12-08 14:39:10