Mystic Number Guesser MS Excel Spreadsheet is a little application that uses mathematics to guess a number that you've picked. I thought I was pretty clever in coming up with this, but I just recently found another, very similar use of the same concept, so I'm sure the idea has been around for some time.
I would like to type a quick explanation of how it works, but haven't had the time. Besides, the opportunity rarely presents itself in class for me to explain such a concept.
The trick is based on modular arithmetic. Modulo 9, in particular.
I hope enjoy.
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