Wednesday, October 04, 2006

Do reporters know anything about math?

The AP's latest obvious mathematical error in a story about math occurs in this article about a Japanese man reciting pi to 100,000 decimal places. The basic facts of the story seem ok, except when the AP reporter (I couldn't find any reporter's name attached to the article) starts editorializing - or more particularly, asserting something as a fact that he/she is purely speculating about. So that's how we get this lovely statement:

"[Pi] is usually written out to a maximum of three decimal places, as 3.141, in math textbooks."

Now, I started out in college as a math major and I was quite the math prodigy before then, taking advanced calculus (that's the "BC" version) as a junior in High School. I still try to keep up on pop math stories, like the latest discovery of the largest Merseinne Prime (those of the form 2^x-1) or the proof of Fermat's Last Theorem (there are no whole number solutions to the equation A^x+B^x=C^x where x is greater than 2). So with my bonafides in place, let me swing away.

First, it is not my experience that math textbooks only write out pi to a "maximum" of three decimal places. It's ususally either 3.14 or 3.1416 or 3.14159 or, getting a little adventurous, 3.141592654. But that's not the true point. Pi written out to three decimal places is 3.142, correctly rounding, not 3.141 (the next two digits being 59, which is more than half so you round up). I suppose if you are reciting the decimal digits and you stop at three you would say "3.141" which brings up an interesting question: did the Japanese guy round off on his last digit? Did he need to? What digit is pi's 100,001th?

In any event, no math textbook would ever write pi as "3.141" which is what the AP reporter said which is beyond ignorant.


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