Professor Phil O’Mathy wrote a long string of symbolic logic on the blackboard, telling his class, “I think you’ll all agree that this is obvious.” Done, he looked at his work once more and his face clouded. “Just a moment,” he said, as he sat at his desk, opened a notebook, and began to scribble furiously. Twenty minutes later, he arose triumphantly. “I was right,” O’Mathy smiled, “It is obvious.”

Mike Schilling

Mike has been a software engineer far longer than he would like to admit. He has strong opinions on baseball, software, science fiction, comedy, contract bridge, and European history, any of which he's willing to share with almost no prompting whatsoever.


  1. Magic trick time:

    Follow along, and I will perform a magic trick by reading your mind. Ready?

    1. Pick a number.
    2. Double it.
    3. Add 14.
    4. Cut it in half.
    5. Subtract the number you started with.

    Your number is………


      • There is no dividing by 0.

        1. Pick a number X.
        2. 2X
        3. 2X + 14
        4. X + 14/2
        5. 14/2

        • Let x = 1.
          Square both sides: x2 = 1
          Subtract 1 from both sides: x2 – 1= 0
          Factor: (x+1)(x-1) = 0
          Divide both sides by (x-1): x-1 = 0
          Substitute the value of x: 1 + 1 = 0
          Conclusion: 2 = 0.

          Since 2 – 0, and you divided by 2 in step 4, you divided by 0.


          • I think you are confusing “Double it” with “Square it”.

            Double it = 2 times X

            Square it = X times X

          • I can’t do superscript. Just pretend the 2 is levitating.

            If it’s equal to zero, it probably weighs a lot less.

          • Ok, then I think some of your +’s and -‘s are wrong in certain places in your forumlas.

            And, regardless:

            Let x = 1.
            Divide both sides by (x-1): x-1 = 0
            Divide both sides by (1-1)
            Divide both sides by 0

            Aha! I’m not the one who divided by zero. You are!

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