Stage: 3 Challenge Level: 
Two circles are enclosed by a rectangle 12 units by x units.
The distance between the centres of the two circles is x /3 units.
How big is x ?
Mathematical reasoning & proof. Radius (radii) & diameters. Circle theorems. Angle properties of shapes. Area. Circles. Short problems. Visualising. Arcs, sectors and segments. Pythagoras' theorem.
Published March 1999.
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
