## Posts tagged ‘pi day’

### Einstein > π

Yes, today is Pi Day.

Whatever.

More importantly, it’s the 134th anniversary of Albert Einstein’s birth. (Isn’t it remarkable that people who celebrate Pi Day don’t think to add a few candles to the pie and sing *Happy Birthday* to Big Al?) It’s interesting that 134 shares the same three digits as Einstein’s birth date, 3/14, and 134 also has the following property:

1 + 3 + 4 = 8

_{8}C_{1}+_{8}C_{3}+_{8}C_{4}= 134

On his birthday, we can honor Einstein by remembering some of his quotes. One of his most famous is about his math ability.

Do not worry about your difficulties in mathematics. I can assure you that mine are still greater.

Slightly less well-known is the following quote by Einstein, also about math.

God does not care about our difficulty with numbers. He integrates empirically.

But special for today, the following is a quote not *from* Eistein, but *about* Einstein. The quote is attributed to a Japanese cartoonist, Ippei Okamoto, and appeared in *Driving Mr. Albert* by Michael Paterniti.

He [Einstein] has a quiet way of walking, as if he is afraid of alarming the truth and frightening it away.

A beautful quote for a beautiful mind. Happy Birthday, Mr. Albert!

### What Dates are Mathier than Pi Day?

While I am grateful that Pi Day gives some much-needed publicity to math, it’s a contrivance like textbook problems about two trains approaching from opposite directions. (Honestly, rather than spend your time determining how long until two trains on the same track collide, why not use that time to inform someone about the imminent collision?) Other than containing the same digits that appear in 3.14, there’s nothing terribly special about 3/14. And it propagates the widely held belief that π is only known to two decimal places.

That said, the cultural significance of Pi Day cannot be overstated. (Or maybe it just was?) Consequently, there are **six cool Pi Day cards at Illuminations** for you to share with friends via Facebook, Twitter, and Pinterest, or download them and include them in an email, on your website, or in a blog post. This one is my favorite:

Recently, there has been a movement to replace π with τ = 2π. (See The Tau Manifesto.) That would suit me just fine, and then we could celebrate Tau Day, which occurs on the more mathematical date 6/28. In addition to 6.28 representing the value of 2π (to two decimal places, anyway), it is also the case that both 6 and 28 are perfect numbers (the sum of their proper factors is equal to the number itself), and this year the value of the month, date and year of 6/28/12 are all even.

Please understand, my disdain for 3/14/12 is not personal. It’s just that other dates this year are, well, *mathier*.

Christmas Eve is one of those mathier dates…

- When written as 12/24/12, all of
*mm*,*dd*and*yy*are even. *mm*+*yy*=*dd*- Each of the digits within the date (1, 2, and 4) are powers of 2.
- The sum of the digits is 1 + 2 + 2 + 4 + 1 + 2 = 12, and 122412 ÷ 12 = 10,201 = 101
^{2}.

…as is the ninth of June…

- The numbers 6, 9, 12 form an arithmetic sequence.
- All three numbers are multiples of 3.
- The month (6) is a perfect number, the date (9) is a square number, and the year (12) is the smallest abundant number.

What do you think is the mathiest date of 2012? And what criteria do you use to determine if a date is mathy?

### Happy 100/9 Day

Today is a special day indeed. You may have already noticed that today’s date is the repetitive 11/11/11, but did you know that **today is the only date this century that can be written in the form mm/dd/yy with one digit repeated six times**?

Some people celebrate 3/14 as Pi Day, and to ensure complete precision for their celebration, the moment at which they celebrate is 1:59:26 p.m. In a similar vein, I suggest that we all celebrate “100/9 Day” at 11:11.11 a.m. today. Too bad 100/9 doesn’t have a Greek letter nickname for which it is better known…

Not too long ago, I was forwarded an email that contained several pieces of numerical trivia. The first was this:

This year we’re going to experience four unusual dates: 1/1/11, 1/11/11, 11/1/11, and 11/11/11.

Today is one of those dates, and it is certainly unusual for a date to contain only one repeated digit. The only other dates with just one repeated digit during this century are 2/2/22, 2/22/22, 3/3/33, 4/4/44, 5/5/55, 6/6/66, 7/7/77, 8/8/88 and 9/9/99. Since there are only 13 dates that contain just one repeated digit, it could also be said that 2011 is an unusual year for hosting four of them.

The email also contained the following:

Take the last two digits of the year in which you were born. Now add the age you will be this year. The result will be 111 for everyone in the whole world.

Blanket mathematical statements like this one are frustrating, especially when they are untrue. My friend’s grandfather was born in 1899, so he will turn 112 this year. For him, the result is 99 + 112 = 211. And my sons were born in 2007 and turned 4 this year. For them, the result is 7 + 4 = 11. In fact, based on data about age distribution, the result will **not** be 111 for approximately 15% of the U.S. population. The yellow bars in the graph below indicate the ages for which this trick does not work.

A better statement of this “trick” might be…

Take the year in which you were born. Now add the age that you will be this year. The result will be 2011 for everyone in the whole, wide world.

Wow! Can you believe it? But it’s not much of a trick anymore, is it?

Happy 100/9 Day, everybody!

**[Update]** This post originally appeared as “Happy 10/9 Day,” but that was in error. I blame sleep deprivation. It has been updated to “100/9 Day” in all places.

### 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*.”

### Jokes for Pi Day

Today is Pi Day (3/14) as well as Albert Einstein’s birthday. Numerologists surely believe that’s no coincidence.

Here are a couple of jokes for today:

- I’m like pi… irrational, but well‑rounded!
- What is the ratio of the circumference of a jack‑o‑lantern to its diameter? Pumpkin pi.