Stage: 3 Challenge Level: 
Mark four points on a flat surface so that there are only two different distances between them. One arrangement is as shown.
How many more can you find?
Are you sure that you have them all?
Click here for a poster of this problem
Squares. Games. Generalising. Creating expressions/formulae. Visualising. Cubes. Mathematical reasoning & proof. Working systematically. Interactivities. smartphone.
Published September 2005.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk