Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

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**ryos****Member**- Registered: 2005-08-04
- Posts: 394

The blogger "ridiculous fish" has implemented a very novel approach to cutting out comment spam (and much better than the "distorted image" method). I thought it was both interesting and cool. Have a look:

http://ridiculousfish.com/blog/?p=23

*Last edited by ryos (2006-04-23 15:04:19)*

El que pega primero pega dos veces.

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,684

So far they have:

* 1359 / 2475 pairs were relatively prime.

* pi is approximately 3.30562434615

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

Pretty interesting.

IPBLE: Increasing Performance By Lowering Expectations.

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**krassi_holmz****Real Member**- Registered: 2005-12-02
- Posts: 1,905

Here's a Mathematica fuction which makes n tests with numbers less than b:

```
PPr[n_, b_] :=
(
c = 0;
Do[If[GCD[Random[Integer, {1, b}], Random[Integer, {1, b}]] == 1, c++;], {i, 1, n}];
c/n
)
```

6/pi^2=0.607927

As you see, this method is unusable, because for approximately 3 digits of 6/pi^2 you need >10^6 tests.

IPBLE: Increasing Performance By Lowering Expectations.

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**Patrick****Real Member**- Registered: 2006-02-24
- Posts: 1,005

well, one million comments, that's not that much

He's just trying to make a laugh of spam (but ruining his fun is great too )

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,684

Good work, krassi!

Another (of the many) ways to calculate π would be to pick a random coordinate in a square, then see if it falls within the inscribed circle (using x²+y²=r²).

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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