Circumference and Area of a Circle: Introduction

Man measuring a track with a circular measuring wheel

Have you ever seen one of these measuring wheels?  By rolling it along a length to be measured and counting how many rotations it makes, the distance can easily be calculated.  The wheel might make ten complete rotations, or it might make nine complete rotations and then another 90 degrees.  Either way, with a few simple geometry calculations, the distance can be found very accurately.  These tools are used to accurately mark distances for races, to accurately measure for building a house, or to find exactly where lines should be painted on a road.  Although this appears to be complicated, once you complete this section, you will be able to use one of these measuring wheels easily.