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It’s not that hard

Letter from John Doe

Math – April 2002 – Colorado Central Magazine

Dear Editor:

I was in about the ninth grade when I took a class in typing. We were told to do a;sldkfjghfjdksla; to strengthen our hands and I did a lot of it. We were farmers and short of typewriters at home so I went in to class early and practiced a bit. There were daughters of merchants and professors and they seemed to catch on some faster.

After a couple of months it became clear that I could hope to learn the topic in time, so I informed the instructor that my folks and I had decided to buy a typewriter. He said, “Well, good!” in a tone of voice which echoes to this day (some 48 years later) — somewhere between a sarcastic “Well you lightweight nerd” and Mr. Burns’ response to Homer’s request for a raise. We did buy a typewriter, a Smith-Corona Sterling portable, and at my peak, some 30 or 40 years ago, I could type almost 35 words per minute on it.

You were asking how do math phobics avoid stupid errors. Brings me back to a class in engineering mathematics in the late ’50s when some nameless instructor gave us a week or so of “dimensional analysis.” Now, I’ve already blown it because when one uses them big words, the math phobic’s eyes cloud over and their brain turns to sawdust. But it is not too hard, and helps catch many silly errors. You just carry the units along with the numbers and make sure that the units make sense at the end. So if there are 8 peas/pod and 64 pods/plant, and 45,000 plants/acre and 32 peas/ounce and 16 ounces/pound, how many pounds on 4 acres? Well you know the answer is going to be pounds of peas so all the other units (“dimensions”) have to cancel out. We don’t want any ounces or plants or acres or pods in the answer, just pounds.

So if I multiply peas/pod times pods/plant times plants/acre times acres, the pods, the plants and the acres cancel out and I’m left with peas. Good, but we don’t want peas, we want pounds. So we divide peas by peas/ounce — this gets a little tricky here because the peas cancel and the ounces show up upstairs — and divide the result, ounces by ounces/pound we wind up with — voila! — pounds. The calculation of this result is left as an exercise for the reader.

John Doe


[Editor’s Note: This letter should have run two months ago, but it somehow got sandwiched between several dozen pages of faxed political information that came in at about the same time. Our apologies for the error. The writer of the letter prefers that his real name not be used.]