WHY DOES THIS WORK??
http://www.niehs.nih.gov/kids/mindread/psychicSparkle2.swf
It worked 8 times for me. I tried it 9, and the only reason it didn’t work once is because I did the math wrong.

Very strange (not the part about me doing the math wrong, the Flash Psychic Ball!).

It has something to do with the tricky number 9.

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Spoiler — after I went back and looked a little harder (block the text below and you should be able to read it):

Okay, I get it. There are only a certain number of ways this can come out. The only possible answers are 81,45,18,63,51, 36, 56,54,69,27,9,72,20,76,6. So if it changes the symbols for each correct number each time it still looks like magic.

Cool!