# Settling a circular argument: room for one more?

By using a regular hexagonal arrangement it is simple to fit 19 identical circles into a larger circle of five times the radius with no circles overlapping. This leaves an area equal to six smaller circles uncovered. Is it possible to rearrange the 19 circles to accommodate a twentieth circle of the same size into the larger one (also with no overlapping of course)?

• I am not completely convinced that this question is of the right level of discussion for this website; but I am not convinced either that it is not. Can you provide more motivation for the problem? (Is this known to be open, historically interesting, or is this just a puzzle? In the last case this question should be asked at Art of Problem Solving, not here.) I've started a meta thread here tea.mathoverflow.net/discussion/533/… Commented Jul 22, 2010 at 0:08
• I apologise if the question is of the wrong type for this site, but having failed to find any way of answering it myself I Googled a page which led me here. It has no use unless I was trying to market an executive toy that asked people to try and slot in a twentieth circle! Commented Jul 22, 2010 at 0:20
• Like I said, I don't know whether it is appropriate, because I am not sure (until I saw Gerry's answer) whether this problem has research interest at all! It'd be better for you (in the future) to pre-emptively squash those qualms by including more background or describing what you've found or why you've come across the question. Commented Jul 22, 2010 at 10:11
• I'd suggest retitling the question since "circular argument" usually doesn't refer to an argument about circles! Commented Jul 22, 2010 at 14:12