Newsgroups: rec.puzzles
From: hoey@zogwarg.etl.army.mil (Dan Hoey)
Date: 22 Mar 91 19:44:49 GMT
Subject: Re: seeing the trees for the forest (correction)

This is a corrected version of my previous article.

jadah...@acsu.buffalo.edu (jason a dahlin) writes:

>Arrange 10 trees so that they form 5 rows of 4.

As I noted some years back, this problem is easier to solve than to
fail at solving.

Spoiler follows...

Pick five [not four] lines in the plane.  If you were so unlucky as
to pick two parallel or three that intersect in a point, you lose.
Otherwise put the trees at the intersections.

Dan

[I am grateful to Robert Ebert for noting the error in the previous
version.  I am not particularly grateful for his posting of its
contents without the spoiler warning or the form-feed. -- DH]