This is a real cool game. It just seems like magic.

  1. You choose a 3 or 4 digit number
  2. Jumble the digits in the number to get a brand new one
  3. Subtract the smaller one from the bigger one
  4. Ommit one digit from the result and tell fido about the other digits
  5. He reads your mind and BOOM, he knows that number you ommited

Give it a try here. If you are not into the phsycic powers of Fido, there’s another options. It’s a simple math game with a proof !

I don’t really know about the proof but you’ll find that the difference between the 2 numbers is always divisible by 9 so the digits of the difference should sum up to a multiple of 9. This way Fido can guess the missing number.

For more about this explanation check the comments on this site.