Interesting and easy math game

[Ghoulish Delight]

Originally Posted by scaeagles

I was able to figure out the secret to that one after just 2 tries. I still can't figure out the math behind the one I posted and why it works every time. Except for WB. I'm think the problem isn't with the game, though, WB.

Well, if X=the first 3 digits of your phone number and Y=the last 4, then your phone number can be represented as 10000X+Y

So, the operations you perform look like this:

(80X+1)*250+2Y-250
___________________
2

Simplifying the numerator, you get 20000X+250+2Y-250.

The +250 and -250 cancel out, leaving you with 20000X+2Y. Divide that by 2 and you get 10000X+Y, which of course is your phone number.