More Math Mindreading


Godzilla is a well-known mind-reader, and in honor of final exams, which are coming up sooner than seems possible, he’d like to demonstrate his powers.  Even over the internet, because his powers are MIGHTY.  Like him.

Start with 3-digit number that is not a palindrome (so 360 is OK, but 363 is not).    Then reverse the digits, and subtract the smaller number from the larger.  You get a NEW AND IMPROVED number.  So if you do start with 360, your NEW AND IMPROVED number will be 297 (which is 360 minus 063).

Treating your NEW AND IMPROVED number as a 3-digit number, reverse the digits.   This means that if your NEW AND IMPROVED number appeared to only have two digits, or even one, then you have to tack on one or two leading zeros that you include in the reversal.

Now add your NEW AND IMPROVED number to its reverse.  Godzilla will now tell you the sum, even over all the miles and electrons that separate you from this friendly beast…..

Poor 1089 doesn’t look like it’s having a very good day.  But he’ll be the star of the show if you do this trick yourself, with super mindreading powers passed along by the Big Lizard himself.

If you want to avoid the whole “leading zero” thing, you can insist that the first and third digits of your starting number are at least two digits apart, which sounds unduly complicated, or that the digits are all increasing [or all decreasing], which sounds slick.  It’s not really necessary, though.

Hat tip to Michaela Stone and Michelle Zajac from Alfred University:  they didn’t invent this trick, but they did share it in a talk at the MAA Seaway Conference at Naz earlier this month.


One Response to “More Math Mindreading”

  1. Dash Says:

    Blowin’ my mind, man.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: