December 4–December 10, 2007

Problem

Pick m points on the positive x-axis and n points on the positive y-axis. Draw a line segment from each of the points on the x-axis to each of the points on the y-axis. Assume that no three lines meet at a point except at endpoints. Excluding the endpoints, how many points of intersection are there?

Solution

here.

List of solvers

Correct solutions:

Dustin Moody, Gary Raymond (graduate); Rich Bauer (alumni).

Rich Bauer wins the prize!