## A Cool Quick Trick for Pi Day

To some extent, I’m anti‑Pi Day. I think it has to do with the predictability of celebrations — everyone serves pie, does circle problems, and says things like, “I’m like π: irrational, but well-rounded!”

So, I was thinking that I would boycott Pi Day this year by not posting anything about the holiday on the MJ4MF blog. Then I discovered a cool trick. It was attributed to Martin Gardner on a web site, but I can’t verify the source. I think I’ve read every book by MG, and I’ve never seen it before.

Anyway, here’s the trick.

Write all 26 letters of the alphabet, but start with the letter J:

JKLMNOPQRSTUVWXYZABCDEFGHI

Then, remove all the letters that have vertical symmetry:

JKL   N   PQRS            Z   BCDEFG

Now, count the letters that remain in each subset: 3 1 4 1 6.

When I did this trick at a K‑12 math teachers’ conference recently, I wrote the numbers under each group. But I wasn’t sure that everyone would recognize the digits. So I drew an exaggerated decimal point between the 3 and 1, and I stated, “If you don’t know why this is relevant with Pi Day just around the corner, you’ve really missed the point.”

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• 1. xander  |  March 13, 2011 at 11:07 am

I am totally with you on the anti-Pi Day thing. Of course, that is only because I prefer Pi Approximation Day in June. 22/7 is so much nicer than 3.14. 😛

• 2. venneblock  |  March 13, 2011 at 12:52 pm

Xander, I think Pi Approximation Day occurs in July, since July is the 7th month.

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