How many digits of Pi do you know?

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Re: How many digits of Pi do you know?

Postby smw543 » Tue Apr 14, 2009 7:00 am UTC

*Double checks with Google*

I thought I knew 24 digits, but I missed the 13th. I guess that technically makes it twelve, though I got the rest of 14-24 correct. (In my defense, the only advanced math I've done in over a year has been for science classes, and we always get to use our calculators...I'm so ashamed :oops: )

But more importantly, this is my π(314th) post!
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Re: How many digits of Pi do you know?

Postby a Person » Thu Apr 16, 2009 12:24 am UTC

OK, so here's my "rhythm" for pi:
3.14159 26535 8979 3238 46264 33832 7 9502884 197169 3993 751 058 2 097 4944 5923078 1640628 6208998 6280348 25342 11 706798 2148 08651 32823 0664 5505 8223 172 535
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Re: How many digits of Pi do you know?

Postby Kurushimi » Thu Apr 16, 2009 2:24 am UTC

3.14159 26535 897 93238462 64338327 9

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Re: How many digits of Pi do you know?

Postby miles » Thu Apr 16, 2009 10:03 am UTC

3. 1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 8214808651 3282306647 0938446095
not fair though since i reviewed my pi after seeing this, memorized in sets of 10 like phone numbers

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Re: How many digits of Pi do you know?

Postby MarcyMarc » Thu Apr 16, 2009 11:19 pm UTC

bored in programming class, ms calc only has thirty some digits

3.14159 26535 8979 323 846264 3383 2795

*897 is the 1st 3 digits of my phone #

*275 (from 2795) is one of my friend's 1st three digits
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Re: How many digits of Pi do you know?

Postby anna95 » Sat May 30, 2009 10:38 am UTC

i learnt 21 digits of pi just reading a poster in my maths classroom, but then i learnt another 3

3.14159265358979323846264

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Re: How many digits of Pi do you know?

Postby thicknavyrain » Sat May 30, 2009 12:21 pm UTC

3.14159265358979

I used to know it to only 3.1415926535 but then I realised that wasn't properly rounded so I kept going until I found a digit with a digit lower than 5 after it, (hence the extra 8979).
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Re: How many digits of Pi do you know?

Postby fwlbg » Sat May 30, 2009 10:05 pm UTC

I remember it more easily in binary (to 64 bi-mal (?) places), even though it's just "1"s and "0"s, and you need more binary digits to approximate pi to the same level of accuracy (or is it precision?) than with decimal digits:

11 . 001001 0000 111111 01101 0101 00010001 0000 101101 00011 0000 1000 1101 0011

Srsly.

Maybe I should learn it to many places in hexadecimal instead, then it would be more accurate (precise?) than with the same amount of decimal digits.

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Re: How many digits of Pi do you know?

Postby potatoman » Sun May 31, 2009 4:05 am UTC

I know about 200ish. 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679 8214808651328230664709384460955058223172535940812848111745028410270193852111055964462294895493038196... I used to know 400 but I forgot a few.

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Re: How many digits of Pi do you know?

Postby Yakk » Tue Jun 02, 2009 4:03 pm UTC

thicknavyrain wrote:3.14159265358979

I used to know it to only 3.1415926535 but then I realised that wasn't properly rounded so I kept going until I found a digit with a digit lower than 5 after it, (hence the extra 8979).

But what digit lower than 5 is it? Huh?
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Re: How many digits of Pi do you know?

Postby brakos82 » Fri Jun 05, 2009 8:53 pm UTC

I am Brakos, and I may or may not approve this message.

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Re: How many digits of Pi do you know?

Postby John_S » Fri Jun 12, 2009 5:33 pm UTC

3.1415926535897932384626433

25. (26, if you count the 3)

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Re: How many digits of Pi do you know?

Postby cpp789 » Fri Jun 12, 2009 9:18 pm UTC

I know 2^8 (256) digits after the decimal point. I've found that if I run through them in my mind at a constant rate, it takes almost exactly 60 seconds (with a standard deviation of 5). As long as I'm doing a fairly repetitive and thoughtless activity, it works pretty well as a timer.

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Re: How many digits of Pi do you know?

Postby The EGE » Sat Jun 13, 2009 2:51 pm UTC

3.14159265358979323846264338327950288419716939937510....

50 digits past the decimal point. I could do 100 for a while, and at one point I knew 250 for a few days. Then I had to say it in spanish for a competition... mental number conversion ftw.

*goes out to memorize a bunch more*
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Re: How many digits of Pi do you know?

Postby WazirKnightBishop » Mon Jun 15, 2009 7:42 am UTC

I could do all the way up to this far: [1 double linebreak per 5 lines]

3.14159
26535897
93238462
643383279
50288419
71693993

75105820
97494459
23078164
06286208
99862803

48253421
17067982
01808651
32823066
47083844

60955058
22317253
59408128
48111745...

19 × 8 + 1 - 2 = 151 d. p.

To be honest, I got hold of a song that just starts 3.14159... and goes on and on. Once you get the rhythm (8 or 9 digits per line) it's quick.
~~~~

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Re: How many digits of Pi do you know?

Postby The EGE » Fri Jun 19, 2009 5:36 pm UTC

3.1415926535897932384626433832795028841971693993751058209749445923078164...

70 now.

I tend to memorize in blocks of 5, mostly. The first 20 are in pairs, though, and 61-70 i think 592307 8164.
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Re: How many digits of Pi do you know?

Postby capncanuck » Mon Jun 22, 2009 5:10 am UTC

Personally: 3.14159265358979323846264338327950288419716939937510582097494459230781

Pi Song, the song without a chorus

And an old web page I found: http://www.albanyconsort.com/pi/

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Re: How many digits of Pi do you know?

Postby Gaydar2000SE » Mon Jun 22, 2009 6:29 am UTC

I know all digits, '10', but I always write π in a positional numeral system with a radix of π to cheat. I have Greek installed so I can be awesome, και συ, τεκνον;

Besides, the most efficient algorithms to compute π always return the string in hexadecimal, and numbers always look 'simpler' in that, I guess it's ultimately better than decimal. It's also 2^2^2 and all...
^ :/

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Re: How many digits of Pi do you know?

Postby gmalivuk » Mon Jun 22, 2009 6:44 am UTC

Yes brilliant and hilarious and you're only about the 40th person to point out that you've memorized the digit of Pi in base Pi ha ha ha.
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Re: How many digits of Pi do you know?

Postby Gaydar2000SE » Mon Jun 22, 2009 8:08 am UTC

Oh well, I can probably come back with some ad hominem saying that you're then at least the 10^40th person to point out that's it done before but I'll go cry I guess, Scotty, hand me the razor.

edit: I shall try to be slightly more original by memorizing it in an ln(-1)/i base next time.
^ :/

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Re: How many digits of Pi do you know?

Postby Dew_N_O » Mon Jun 22, 2009 8:23 am UTC

I know all the digits of pi:

10.

See, I use a base of digits that makes it so that when you start to talk about things, the things change right in front of you.

I use a base of digits that makes people suffer that shouldn't.

Oh wait that happens without a base or any good reason.

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Re: How many digits of Pi do you know?

Postby TheGuyWithTheHat » Wed Jul 22, 2009 8:49 am UTC

64. I also like the number 64 because it's one of the "flash memory numbers" and it's even and a multiple of two, plus half 64 is 32 and that's my lucky/favorite number.
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Re: How many digits of Pi do you know?

Postby Orkimond » Wed Jul 22, 2009 11:27 am UTC

I used to know 120 digits, learnt it for a school comp, but now I only know 60 or so.

Here's a question, does pi contain, by the nature of it's irrationality, a string of arbitrary length of the same digit within pi?

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Re: How many digits of Pi do you know?

Postby PM 2Ring » Wed Jul 22, 2009 12:18 pm UTC

Orkimond wrote:I used to know 120 digits, learnt it for a school comp, but now I only know 60 or so.

Here's a question, does pi contain, by the nature of it's irrationality, a string of arbitrary length of the same digit within pi?

Possibly, but we don't know for certain. http://en.wikipedia.org/wiki/Normal_number
Wikipedia wrote:In mathematics, a normal number is a real number whose digits in every base show a uniform distribution, with all digits being equally likely, all pairs of digits equally likely, all triplets of digits equally likely, etc.

While a general proof can be given that almost all numbers are normal, this proof is not constructive and only very few concrete numbers have been shown to be normal. It is for instance widely believed that the numbers √2, π, and e are normal, but a proof remains elusive.

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Re: How many digits of Pi do you know?

Postby Piogre » Wed Jul 22, 2009 5:16 pm UTC

I've known 70 digits since the 6th grade:

3.1415926535897932384626433832795028841971693993751058209749445923078164

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Re: How many digits of Pi do you know?

Postby MidsizeBlowfish » Tue Aug 11, 2009 9:38 pm UTC

3.14159

Six. If I wanted to know more, I'd ask a computer.

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Re: How many digits of Pi do you know?

Postby Kurushimi » Tue Aug 11, 2009 10:39 pm UTC

Does anyone know any good programs for memorizing digits of pi?

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Re: How many digits of Pi do you know?

Postby mimizu » Wed Aug 12, 2009 7:47 am UTC

3.14 159 2653 58979 3238 462 643 383 279 50288 41...

And then I messed. :cry:

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Re: How many digits of Pi do you know?

Postby minno » Fri Aug 14, 2009 12:32 am UTC

Posted without looking at any other posts besides the opening one:

3.14159265358979323. 17 digits after the decimal point.

The only time I actively tried to memorize them was on pi day in 8th grade (march 14, 3/14). I used to know about 10 digits after that, but it's been 3 years.
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Re: How many digits of Pi do you know?

Postby RabidAltruism » Mon Aug 17, 2009 3:40 am UTC

3.14159265 .. and then I can never remember whether a 3 or a 4 follows next.

I thought I was doing pretty well at that length! Seems I've got a long way to go on my pi mnemonics is I want to be competitive 'round here. :mrgreen:
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Re: How many digits of Pi do you know?

Postby achan1058 » Wed Aug 19, 2009 4:30 am UTC

3.141592, despite the fact that I am going to be a mathematician. (a grad student currently) As said above, if I want more digits I get the computer.

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Re: How many digits of Pi do you know?

Postby Scip » Thu Aug 20, 2009 8:14 pm UTC

3.1415926535987932384626433 - 21, including the 3. I used to know 30 digits after the decimal point for pi day in 9th grade. When I'm bored nowadays, sometimes I'll just memorize a couple more digits from the Windows scienfitic calculator...

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Re: How many digits of Pi do you know?

Postby PM 2Ring » Fri Sep 25, 2009 2:51 pm UTC

I just "discovered" an interesting interpolation for the Wallis product formula for pi. I don't think this deserves a new thread, and this seems like a good place for it.

The Wallis product formula is
[math]\prod_{n=1}^{\infty} \frac{(2n)(2n)}{(2n-1)(2n+1)} = \frac{2}{1} \cdot \frac{2}{3} \cdot \frac{4}{3} \cdot \frac{4}{5} \cdot \frac{6}{5} \cdot \frac{6}{7} \cdot \frac{8}{7} \cdot \frac{8}{9} \cdots = \frac{\pi}{2}[/math]
Note that successive partial products alternate above and below the limit. So it's likely that interpolating between them will give a good pi approximation.

Also note that terms can be grouped into pairs in two ways:
[math]\frac{n^2}{n^2-1} \mbox{ for even n}[/math] or
[math]\frac{n^2-1}{n^2} \mbox{ for odd n}[/math]
The second form is useful because we can divide n² out to give (1-1/n²).

I have found that by calculating upto a term of the form [imath]\frac{2n}{2n-1}[/imath] & interpolating between the last two products, that a much better approximation to pi can be found. Let p be a partial product with the next term being [imath]r = \frac{m+2}{m+1}[/imath]
Next we find a & g, the arithmetic & geometric means respectively of p & pr.
Then a - g is very close to pi - a. So 2a - g is a good pi approximation.

Here's a short bc program that illustrates this technique. Note that m must be even for this to work properly.

Code: Select all

scale=30;m=5000;p=4*m/(m+1);for(i=3;i<m;i+=2)p-=p/(i*i);r=(m+2)/(m+1);p*(1+r-sqrt(r))

The above code yields 3.141592653589793630690807651016

Proof of why this method works will be left as an exercise for the reader. :)

Of course, this algorithm is rather slow compared to the Arithmetic-Geometric Mean algorithm (and other formulae discovered by Ramanujan), or even some good arctan-based formulae, but apart from one square root most of the arithmetic is very simple.

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Re: How many digits of Pi do you know?

Postby Elusieum » Fri Sep 25, 2009 4:48 pm UTC

3.14159265358979323...

18 digits. =)

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Re: How many digits of Pi do you know?

Postby Spen » Sat Sep 26, 2009 8:05 pm UTC

3.141592
As Much as I know, a maths teacher in my school knows 65 and a kid in his class is trying to beat that.

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Re: How many digits of Pi do you know?

Postby BlackSails » Sun Sep 27, 2009 4:27 am UTC

MidsizeBlowfish wrote:3.14159

Six. If I wanted to know more, I'd ask a computer.


This.

If I want more, ill ask wolfram|alpha for it. If I really need more and dont have a computer, then just start running the taylor series for arctan

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Re: How many digits of Pi do you know?

Postby chridd » Sun Sep 27, 2009 5:00 am UTC

3.14159 26535 8979 323 846264 3383 279502 884 197169 399 375105 820 974944 59230 78164 06286208 998 6280
86, if I counted right
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Re: How many digits of Pi do you know?

Postby Ran4 » Sun Sep 27, 2009 4:55 pm UTC

3 14 159 26 53 5 8979 323 846 26 433
25 digits? Thought I usually stop at 43, to avoid huge rounding errors.

...oh, and one awesome thing I just found out: writing "p" in the windows calculator is actually the same as pressing the pi button. Awesome! (found out when I tried to write "pi").

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Re: How many digits of Pi do you know?

Postby thicknavyrain » Fri Oct 23, 2009 4:56 pm UTC

Yakk wrote:
thicknavyrain wrote:3.14159265358979

I used to know it to only 3.1415926535 but then I realised that wasn't properly rounded so I kept going until I found a digit with a digit lower than 5 after it, (hence the extra 8979).

But what digit lower than 5 is it? Huh?


3 and then a 2!

That's as much as I can remember now. Just for you.
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Re: How many digits of Pi do you know?

Postby Mavrisa » Thu Oct 29, 2009 9:22 pm UTC

Gaydar2000SE wrote:edit: I shall try to be slightly more original by memorizing it in an ln(-1)/i base next time.


Ohhh you're a clever one aren't you... :P

I know someone mentioned phi and e as well and that made me excited, so here goes:

pi:
3.14159265358979323846 soo 21 including the 3.
phi:
1.618 *sad*
e:
2.718281828459045235360287471352662497757247093699959574966967627724076630353547594571382178525166427427466391932003059921817413596629043572900334295260595630732328617... ummm.. no that's all I got. Thought I knew a few more.
My friend and I had a digit memorizing contest and I wanted to be different. Hopefully that's all right..

Edit: Heh, so I did get some wrong but it was cut off anyway. :roll:
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