Amaze your friends, win the million dollar challenge...

[hard_head]

A psychic webpage that will amaze and amuse.
Confuse your co-workers, win some cash.

Psychic Webpage (http://www.cyberglass.co.uk/assets/Flash/psychic.swf)

[MRC_Hans]

Funny, it works some of the time, other times its consistently off. I think I read about this trick, but I dont remember the details.

Hans

[Stimpson J. Cat]

It's simple. Your number will always be a multiple of 9.

10a + b - a - b = 9a

where a is the first digit (10s place), and b is the second digit (ones place).

They just produce a random sequence of symbols, and make sure that every 9th symbol is the same.

Dr. Stupid

[hard_head]

Indeed, but it is amazing how quickly some folks think the computer is really doing something extraordinary. And then get PO'd when you explain it to them. No wonder psychic hotlines rake in the bucks.

Hans check your math again, I've done it for dozens of numbers and it always works.

[Hellbound]

Stimpy's right. Your final number will always be a multiple of 9:

10-(1+)=9
11-(1+1)=9
12-(1+2)=9
...
21-(2+1)=18
22-(2+2)=18
...
57-(5+7)=45

So, in each iteration, the symbols for 9,18,27,36,45,54,63,72,81, and 90 will be identical.

The symbols for these numbers change each time the page loads, so you get a different "final" symbol each time.

[Underemployed]

I was just wiling away some time when I suddenly noticed that every multiple of the number nine can be reduced to the number nine by adding up the resulting digits.

9 x 9 = 81 ---> 8 + 1 = 9

9 x 4 = 36 ---> 3 + 6 = 9

9 x 65352 = 588168 ---> 5 + 8 + 8 + 1 + 6 + 8 = 36 ---> 3 + 6 = 9

I have not done any proofs for this being correct up to infinity as I have no idea how. But I suspect it would be true for nine times any whole number.

Numbers 1-8 do not have this property. Is there something a real mathematician can tell me about the number nine? I can't be the first person to notice this (this psychic trick is probably based on this property nine has) but I have very little grounding in formal mathematics.

Coincidentally, I was born on the 9th of September...(but not on a year ending nine, drat)

[Hellbound]

Because it's a base-10 system. Same reason the psychic page works as it does.

In both instances, it would be different for a different system. In base 8, 7 would be the magic number. In hexadecimal, F would be it. In base 12, it would be 11, and so on.

It's simply an artifact of the way we write numbers; the fact that we "roll over" to a new column at 10 (in our system).

[jj]

Hey, like wow, man, it's the casting out 9's magic trick!

It is nicely disguised, though. Still all it does is figure out how to subtract the 9's residual from the number, the same way that I used to figure out the residual to test arithmetic.

In any base, it works for the number base-1. In hex, it would be "casting out 'F's"

[Underemployed]

This forum is better than here (http://www.newscientist.com/lastword/) for quick answers! Thanks.

On an aesthetic note, it is easy to spot even if you don't know any maths - the signs are all in neat rows and the numbers make it easy after a few times to see every guess results in a multiple of nine. If I did this trick, I'd arrange them in a pyramid or a spiral and swap numbers for letters. That would slow down any ill-informed skeptics.

[xouper]

bump

[T'ai Chi]

old thread, but what the heck

http://www.statisticool.com/mindreader.htm

is my explanation, and

http://www.statisticool.com/digitalroot.htm

explains a similar but slightly more involved number trick.