# I will go insane if somebody does not explain this to me.

Discussion in 'Community' started by iJon, Feb 7, 2003.

1. ### iJon macrumors 604

Joined:
Feb 7, 2002
#1
My friend and i were browsing the web and i came across this. It is right everytime. I know there is an equation or something. I tried reading the source code but sitll coudnt figure it out. someone tell how it knows this or i will go insane, as well as my friend.

http://www.ebaumsworld.com/mindprobe.html

iJon

2. ### SPG macrumors 65816

Joined:
Jul 24, 2001
Location:
In the shadow of the Space Needle.
#2
It's a simple thing really. Go back and look at the letter given. Then look at how many numbers have that letter. Click it again, and wait, now all those numbers have the new letter.
If you perform the formula to any number it correspnds to a certain set of numbers only. The rest of the letters don't matter.

3. ### iJon thread starter macrumors 604

Joined:
Feb 7, 2002
#3
thanks, i guess i didnt look hard enough, now i can go to sleep.

iJon

4. ### eyeluvmyimac macrumors regular

Joined:
Oct 27, 2002
#4
All they did was go through the possible choices people could end up with (only 14 possible answers) and set them all to them same letter/symbol. That way, no matter what numbers were chosen, and no matter what the result was, the symbol and guess would match up. For example, if you jsut look at the screen and try multiple times without clicking teh square you'll see what I mean.

I tried...

78 - 7 - 8 = 63 --> R
16 - 1 - 6 = 9 --> R
43 - 4 - 3 = 36 --> R

you begin to see the pattern?

Simple as that.

Edit: ok well I was the first reply when I was typing, but unfortunately by the time I clicked send, i was third. lol time is a @*#\$@#

5. ### Mr. Anderson Moderator emeritus

Joined:
Nov 1, 2001
Location:
VA
#5
Its basically always going to be some factor of the number 9 - so all the combinations of 9 have the same symbol, even though that symbol changes from iteration to iteration.

take a look at the chart next time - 0,9,18,27,36, etc. all have the same character.

D

Joined:
Feb 7, 2002
Location:
serendipity
7. ### Mr. Anderson Moderator emeritus

Joined:
Nov 1, 2001
Location:
VA
#7
true, but even more so when you try and 'prove' why its always true for nubers between 10 and 99

Any math geeks out there who can do the proof? I've got an idea why, but can't really explain it correctly.

D

8. ### Moxiemike macrumors 68020

Joined:
Jan 1, 2002
Location:
Pittsburgh, PA
#8
soooooper trippy dood!

9. ### crackpip macrumors regular

Joined:
Jul 23, 2002
#9
informal proof

Say you have a number xy where x is a single digit and y is a single digit. The formula is

xy - x - y => x0 - x

There is only one variable, and therefore there are only 9 possibilities (remember this has to be a 2 digit number) for the difference.

x0 - x => 10 - 1, 20 - 2, 30 - 3, ...

Basically this problem is a reduction of a two dimensional problem to a one-dimensional problem and then listing all the possibilities.

crackpip

10. ### Mr. Anderson Moderator emeritus

Joined:
Nov 1, 2001
Location:
VA
#10
Re: informal proof

That I figured out, but I was more concerned on an appropriate proof where you don't list all the results - that's a quick and dirty way of doing it.

Thanks though,

D

11. ### colocolo macrumors 6502

Joined:
Jan 17, 2002
Location:
Santiago, Chile
#11
I just want to put the same formula given above in a bit more "mathematical" way.

as said before, x and y are single digit numbers.

so:

xy-x-y=10x+y-x-y=10x-x=x(10-1)=9x

thus,

for any number chosen between 10 and 99, the answer will be always in the form of 9x.

12. ### Mr. Anderson Moderator emeritus

Joined:
Nov 1, 2001
Location:
VA
#12
That works for me, thanks. I'm at work and didn't have time to think it through more than determining what the relationship was.

I wonder if there are any combinations for 3 or 4 digit numbers? I have to think about that one.

D

13. ### Shrek macrumors 65816

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Nashville, Tennessee USA
14. ### scem0 macrumors 604

Joined:
Jul 16, 2002
Location:
back in NYC!
#14
Same here, but I haven't even taken Algebra II . I kind of get
it though.

15. ### Shrek macrumors 65816

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Jul 23, 2002
Location:
Nashville, Tennessee USA

Joined:
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Location:
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