A mathematical curiosity

A mathematical curiosity

This is probably an internet meme as old as AOL, but I only just discovered it today. And it’s truly remarkable. Or maybe it isn’t? Feel free to comment, if you know the short explanation.

11 x 11 = 121

111 x 111 = 12321

1111 x 1111 = 1234321

11111 x 11111 = 123454321

111111 x 111111 = 12345654321

1111111 x 1111111 = 1234567654321

11111111 x 11111111 = 123456787654321

111111111 x 111111111=12345678987654321

3 Responses to “A mathematical curiosity”

  1. Matt says:

    You missed out 1 x 1 = 1.

    I always said true beauty can only be found in tragedy, the female form and mathmatics, which I think you’ll agree makes me a particularly well-rounded individual.

  2. Nick Houldsworth says:

    Had Newton and Shakespeare had a daughter, you’d have found your soul-mate..

  3. I hope the formatting works the way I want it to.

    I don’t have a short explanation, just a fun way to think about this visually. Borrowing from Steven Strogatz http://opinionator.blogs.nytimes.com/2010/02/07/rock-groups/

    1×1
    .

    2×2 or 2^2
    . .
    . .

    10×10 or 10^2
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .
    . . . . . . . . . .

    11 x 11 might look like a 10×10 with some more stuff:
    . . . . . . . . . . .
    . . . . . . . . . . .
    . . . . . . . . . . .
    . . . . . . . . . . .
    . . . . . . . . . . .
    . . . . . . . . . . + .
    . . . . . . . . . . .
    . . . . . . . . . . .
    . . . . . . . . . . .
    . . . . . . . . . . .

    + +

    . . . . . . . . . . + .

    That could be represented as:
    the large square block + the left side + the right side + the bottom right part
    so
    10×10 + 1×10 + 10×1 + 1×1
    or
    100 + 20 + 1

    Following that pattern 111×111 might be:
    . . . — 94 more —- . . . + 11 dots
    98 more
    . . . — 94 more —- . . . + 11 dots

    +

    11 dots across + 11×11 square

    100×100 + 11×100 + 100×11 + 11×11
    10000 + 1100 + 1100 + 121

    10000
    1100
    1100
    + 111
    ——-

    1111×1111 becomes
    1000000
    111000
    111000
    12321

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