Math Lab: Casting Out Nines

How do you feel about checking your work after you’ve labored for minutes solving a mathematical problem? Learn this diabolically easy procedure, called casting out nines, right here. Do the problems presented, and learn the password that will take you to the treasure page. This method of checking math calculations is included in Quick and Easy Mathematics, a book written by science fiction author Isaac Asimov.

courtesy of Knovation