Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site uwvax.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!uwvax!anderson
From: anderson@uwvax.UUCP (David P. Anderson)
Newsgroups: net.puzzle,net.math
Subject: Another neat problem from Putnam Exam
Message-ID: <10@uwvax.UUCP>
Date: Sat, 20-Oct-84 02:41:14 EDT
Article-I.D.: uwvax.10
Posted: Sat Oct 20 02:41:14 1984
Date-Received: Sun, 21-Oct-84 14:47:17 EDT
Distribution: net
Organization: U of Wisconsin CS Dept
Lines: 13
Xref: godot net.puzzle:240 net.math:494

<>
This is one of my favorites.

You have sets X and Y of points in the plane, each with n elements.
Assume that no three points in X u Y are colinear.
Prove or give a counterexample: there is a set of line segments,
each of which has one endpoint in X and the other in Y, and of which
any two segments are disjoint.

Hint: the solution is simple and doesn't use any geometry
outside of the triangle inequality.

David Anderson (uwvax!anderson)