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

obviously it cant 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

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
Homework Helper
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 :tongue2:

Thanks kof9595995 that explains it perfectly, isnt algebra wonderful.

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

fleem, thats an interesting site too, very clever.

teheh, all the multiples of 9 are the same gifts