Dimensional Analysis

I told my freshmen they could go home and tell their parents they learned “dimensional analysis” in math today. We’re just converting units — meters to miles, etc. — but it sounds awesome. Your parents’ll be impressed, I said.

In terms of math obsession, I’m somewhere in the bottom quartile of math teachers. I’m low. There are those with the posters that show how every one of the high school math standards — even DeMoivre’s theorem! — is essential to some working sector. It’s phony. You need less math nowadays than ever before.

So I tell the students that math isn’t necessary for their survival. They’ll never find themselves clinging from a cliff with their only means of survival resting on their ability to find the roots of a polynomial. I’m not going to lie to them. But at various points in the year, I make sure they know that having a little math to work with can make life a lot more fun.

Today was one of the hallmark days of my Math Makes Life Fun campaign. After all, dimensional analysis was directly responsible for my Guinness World Record. I can tell ’em this with a straight face because it’s true.

I told my two Algebra classes how I was flipping through the Guinness Book of World Record and discovered that the most paperclips chained in a 24-hr span was 21,073 clips. I asked them, “What’s the question you’ve got to be asking yourself here?”

Hardly any of them ask the right kind of questions. I’ve got to work on that.

When no one responded, I said, “Is that fast or slow? Is it like one clip every ten seconds?” And then I pulled out a box of paperclips — the same ones I’m still burning through from three years ago — and clipped two together. I held up a third clip and counted to ten out loud, while they watched. “One one thousand two one thousand … ”

By “seven one thousand” JG yelled, “Just clip it on!”

So I told him, that’s the point. If it’s that slow, I’m taking the record down. But if it’s one paperclip every second, that’s too fast for me, and the woman deserves her record.

So I took them through the problem.

And we came up with the same number I did years ago: 4.1 seconds per clip. Shamefully slow. And that, boys and girls, is why I decided to break a Guinness World Record.

It’s a good thing I saved this exercise for the last instructional block because at that point class was over. The questions came. I gave answers. I talked about how I made a spreadsheet — again, using dimensional analysis — that allowed me to punch in my progress at a certain moment and project my final count, which helped my friends keep me paced.

A lot of them didn’t believe me but they clearly thought it was a fun story. These days I know all the questions they’ll have — how much did it cost? how did you prove it? are you in the book? — and spin the answers to their best effect. I’m not shy about my methods. I show them how to clip the outer loop over the inner, how using Triadsâ„¢ is really the way to go (remember that, Steve?) if your fingers can handle it. After that, some kid inevitably says he’s going to break it. I tell him, go for it, and I offer my help. There are easier records in the book, I’m convinced. It isn’t in this year’s book and Guinness’ webpage no longer lists it. It’ll be a good lesson illustration for a while.

Even after I pulled up the website and showed them a photo of the certificate, SA didn’t believe me. They’ve seen me run from a tornado in a photograph. My “Fake or Legit” game definitely screwed me over. I promised to bring the book in on Monday. I didn’t really care anyway. The record isn’t the point. Math is out there, and it’s a lot of fun.

I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. He / him. More here.