[Offtopic] Mind Reading Mystery

[Michael Walker]

>>> Rupert Russell<r.russell at ballarat.edu.au> 03/31/05 06:41am >>>
>Dear Roslyn,

>I did a Google search for psychic.swf and found what I assume to be other sites with the same file on them

>see:

>http://demon.twinflame.org/psychic.swf 
>http://www.richhook.com/psychic.swf 

>Look at the number 18  (1 + 8 = 9)  you will see a random symbol next to it.  
>Look at the number 27  (2 + 7 = 9)  you will see the same random symbol
>Look at the number  36 (3 + 6 = 9) you will see the same random sysbol
>then when you click on the crystal ball you see the same random symbol. 
>Looks like magic...


>Hope that helps..

>Rupert.

Or algebraically speaking:

Original number: 10a + b

Add both digits: a + b

Subtract total from original: 10a + b - (a + b) = 10a + b - a - b = 9a

Therefore any multiple of 9 will have the same picture as the ball. In fact, if you added a rule to divide by the multiple of 10 you had originally chosen (ie a), you'd end up with just 9 but it would give the game away rather quickly if you kept getting that as the answer...

In one of the MCTP books, there is an exercise in using Algebra using the psychic number idea.