Newsgroups: sci.math
From: hoey@pooh.tec.army.mil (Dan Hoey)
Date: 11 Nov 1994 18:44:13 GMT
Subject: Re: A Combinatorics Problem.

Kanad Chakraborty (ka...@colorado.eecs.umich.edu) wrote:

> Prove that the maximum number of infinitely long cylinders (in
> R^3, i.e. the 3D real space) of the same radius such that each
> cylinder touches each of the other cylinders, is 6.

Where I come from, we call that a geometry problem.  And oddly enough,
I saw it in Croft and Guy's _Unsolved problems in Geometry_ earlier
today.  I'm pretty sure he said it's one of the unsolved ones.  Seven
can be done if the cylinders are finite, though.

Dan Hoey
Hoey@AIC.NRL.Navy.Mil