Stage: 2 Challenge Level: 
This activity requires some lateral thinking - a bit of fun!
Addition & subtraction. Multiplication & division. Working systematically. Trial and improvement. Combinations. Visualising. Investigations. Factors and multiples. Interactivities. Practical Activity.
Published March 2004,April 2004.
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