Dividing a Circle

Remember that a circle is divided into 360° –  we can thank the Babylonians and their base-60 numeration for that. They counted on the twelve phalanges on one hand, using that thumb, and kept track of the twelves on the other hand. Six groups of sixty approximated the length of a year, and 60 has lots of divisors, so it stuck!


In school you probably used protractors like this one to measure angles. It is divided into 180 degrees. Most protractors have two scales, one reading in each direction. That’s nothing special, it just prevents you from having to turn the paper or the protractor. For lots of kids, it’s just a source of confusion.

I think you could handle turning the protractor!

Turned Protractor



On to π (pi)