How does this website read your mind.

[jacksnap]

Hi ,
A friend sent me this website, and I was wondering how it worked,

http://www.regiftable.com/regiftingrobinpopup.html

obviously it can't read my mind, and its some kind of mathematical trick, I can initially see that all the answers i come up with are 18 apart and that gift is always the same, but why.

Jason

 

[kof9595995]

Hah,it's a liittle tricky.
Any 2-digital number can be expressed as 10a+b,so what you do in fact is 10a+b-a-b=9a, always a multiple of 9, and you notice that the gifts labled by 9,18,27...are always the same!

 

[Mentallic]

haha I liked this

Seriously, its not even like those "think of any number, at 20, multiply by 50, subtract 100... etc." sort of doo-wackies. It's so simple it asks for just one thing from you and gets it right every time. I was so stumped as how it was done, lol post #2 spoilt the fun

 

[fleem]

I've always liked this one:

http://www.cs.williams.edu/~bailey/applets/MindReader/index.html

Because I know a little something about the algorithm I can do pretty good at it, but it still eventually wins.

 

[jacksnap]

Thanks kof9595995 that explains it perfectly, isn't algebra wonderful.

I've just never seen it applied like that before.

fleem, that's an interesting site too, very clever.

 

[Smile101]

teheh, all the multiples of 9 are the same gifts