Nine's Complement Subtraction Method

For any mathematical operation there exists more than one method of carrying it out. This video looks at nine's complement as a method for subtraction that is quite different from the so-called standard method. It allows you to change all subtraction problems into addition problems. In this video I give an introductory example, then additional examples including special cases, and then I finish the video by going deeper and looking into why this method might be used and what is behind the way it works.

FURTHER DETAILS

The first calculating device pictured is Napier's Bones. The set I have is produced by Creative Crafthouse.

The second calculating devices pictured are Pascalines. These were invented by mathematician Blaise Pascal and can be found in the CNAM museum in Paris.

All photographs by Heidi Meyer

Video edited with Clipchamp