Metric to Imperial by and for Dummies

Millimeter to Inch comparison

We've always found it strange that we Americans are so resistant to the idea of metrification, especially given the innumeracy rampant on our side of the pond. You'd think that jumble of conversion factors in the English (Imperial) system – 12 inches per foot, sixteen ounces per pound, 4 quarts per gallon, 5280 feet per mile, and so on – would quickly drive all the Yanks who can't do long division into the simple decimal arms of the metric system; but nooooo... So fifth-graders across the country find themselves turning to the internet for help with conversions. Heaven help them if they turn to eHow's Harry Havemeyer, because here's a guy who's not only wrong ("How to Convert 3.5 Millimeters to Inches"¹), he isn't even consistent ("How to Convert 220 mm to Inches"²): talk about a dumbass!

The answer in both cases is "Divide it by 25.4." If you're so lazy you have to have someone else calculate it for you, you can just type "mm to inches" into a Google search bar and a tool pops right up. The answers to those two "how-to" questions, respectively, are 0.138 inches and 8.66 inches.

But guess what answers Havemeyer got? Apparently, Tulane University doesn't require its PolySci and philosophy students to take either math or science courses, because Havemeyer's "answers" are, respectively, 0.01377952755907 inches and 8.8 inches. We kid you not.

For the 3.5-mm question, Harry (while blathering extensively to meet his minimum word count) instructs the reader to "Multiply 3.5 times 0.00393700787402." That's odd: we remembered the conversion factor between millimeters and inches as 0.03937; and, by golly, we were right. Where Harry picked up that extra zero is beyond us... Of course, as has long been the practice among eHowians, Havemeyer glommed onto a topic and milked it for a few "titles." When asked again later, Harry explained that to convert 220mm to inches, one should: "Multiple [sic] the 220 times 4, which will result in the number 880. Move the decimal point two places to the left since you are actually multiplying the 220 times .04, giving you the answer 8.8..."

That's right, folks, instead of a conversion factor with 14 decimal places (one of which is erroneous), Havemeyer supplies a conversion factor of two decimal places. We know 0.03937 rounds to 0.04, but isn't that conversion factor... we don't know, a little "coarse"?

So much for accuracy (and precision!) in conversions. We began to wonder whether Havemeyer had ever worked for NASA on the Mars Climate Observer project. Or maybe the content editor from eHow did, we can't tell which -- all we know is that for having the temerity to publish not one but two incorrect metric conversion titles and get them wrong in two different ways, Harry is one of the most over-qualified Dumbass of the Day awardees in Antisocial Network history!

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was ehow.com/how_8162783_convert-35-millimeters-inches.html
² This one's original has also been deleted by Leaf Group. Access it with the Wayback machine and URL ehow.com/how_7860750_convert-220-mm-inches.html

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MM - ARITHMETIC