Just like a cool magic trick, it’s kind of a let down once you know how it’s done. So pick a three digit number, reverse the digits,  and subtract the smaller number from the larger:

ABC – CBA =  XYZ

If you end up with a two digit number, include the zero in the hundredth place.

Now reverse those three digits and add them, then look at the title of this thread:

XYZ + ZYA = _ _ _ _

This works great with young kids who know basic arithmetic, especially when you write the number down ahead of time and hide it under the cat. Better yet, write it ON the cat. They’ll be amazed, and you can tell us all about it on The Overnight Open Thread.