## General Math Discussion Topic (not a forum gaaame)

Archive of the first decade of Off Topic Posts
Blast!10
Rainbow Star
Posts: 1732
Joined: Thu Nov 02, 2006 7:26 pm
Location: Tel Aviv

### General Math Discussion Topic (not a forum gaaame)

This topic is to discuss anything and everything math related. Talk about conversion formulas, fun facts, proof, bitwise operators, algebra, and everything else.

Did you know that there's one easy way to find a conversion formula between Celsius and other temperature scales?

First of all, if someone presents you a new scale, he probably tells you the freezing and boiling point of water. In Celsius it's 0 and 100, and in Fahrenheit 32 and 212.

I'll make an example by converting Celsius to Fahrenheit. Celsius will be the "source scale" and Fahrenheit will be the "destination scale".
The first thing you need to do is subtract the destination scale (F) freezing temp (of water) from the destination scale boiling temp. (212-32=180)
Divide the result by [source boiling point]-[source freezing point]. If you'd do Fahrenheit to Celsius, you would divide the result by 212-32=180. Since I'm converting from Celsius, I'm dividing the result by 100-0=100. 180/100=1.8, which means that each degree Celsius is 1.8 degrees Fahrenheit. Of course if you already know the distances between each degree, you can skip this step entirely.

The next step is very simple. If you're converting from Celsius, multiply the source temperature by the "distance" between each degree in the destination scale (in my case 1.8) and add the freezing point of water in the destination scale (in my case 32).

If you're converting to Celsius, subtract the freezing point of water in the destination scale from the source temperature, and divide the result by the "distance" between each degree in the destination scale.

Let's say my temperature was 40 Celsius. In Fahrenheit that would be 40*1.8+32=104.

To convert 104 Fahrenheit back to Celsius, do (104-32)/1.8=40.

Dlcs18 once made a scale called Unfriad, where water boils at 9001 and freezes at -9001. I've found that each degree Celsius is 180.02 degrees Unfriad, and made Celsius-Unfriad and Unfriad-Celsius conversion formulae, all using the method described above.

27 Celsius in Unfriad would be 25*180.02+(-9001)=25*180.02-9001=4140.46.

This isn't very understandable, but I did my best. My country isn't an English-speaking one, so I'm quite unfamiliar with English math terms.  DEEMAN223344
Rainbow MegaStar
Posts: 3145
Joined: Tue Dec 04, 2007 8:07 pm
IT'S OVER NINETHOUSAAAAAAND!!!
~xpr'd~
Rainbow Star
Posts: 1357
Joined: Tue May 12, 2009 9:43 pm
Location: New York
Contact:
g(x)=x^4+2x^3+x^2+8x-12

g(x) = x^4 + 2x^3 + x^2 + 8x - 12

g(x) = (x + 3)(x - 1)(x^2 + 4)

Real zeros are x = -3 and x = 1

The other 2 complex roots are ±2i.

Yet I'm not totally sure :E

and i also suck at writing math
nobody understands mine she/her | Sayori#2285
dlcs18
Rainbow MegaStar
Posts: 3282
Joined: Sun Jul 09, 2006 9:44 pm
EDIT: This is actually useless because it just produces x*y*z. Nothing special.

If you have 3 integers, named x, y, and z, and do this formula with it:
((x*y)/z)*((x*z)/y)*((y*z)/x), you will always get a whole number.

I've tried it with: (number in brackets is the result)
2 3 4 (24)
4 5 6 (120)
6 7 8 (336)
11 12 13 (1716)

I think the reason it's always a whole number is because you are using the same three numbers every time you do (blah*blah)/blah, so the fractions merge together to make a whole number.
Last edited by dlcs18 on Wed Jul 14, 2010 5:23 pm, edited 3 times in total.
dlcs18
Blast!10
Rainbow Star
Posts: 1732
Joined: Thu Nov 02, 2006 7:26 pm
Location: Tel Aviv
Just checked, it works with 125 126 127.

Also, I think you missed a bracket there.
((x*y)/z)*(x*z)/y)*((y*z)/x)
The big bracket has no opening bracket. Is this a mistake?

EDIT: I just checked, and found another error. ((4*5)/6)*((4*6)/5)*((5*6)/4)=120, not 12.
Last edited by Blast!10 on Wed Jul 14, 2010 5:06 pm, edited 1 time in total.
dlcs18
Rainbow MegaStar
Posts: 3282
Joined: Sun Jul 09, 2006 9:44 pm
yes... fix'd
EDIT: Oh, ok. I guess that explains why at first the results seemed to be going up and down. Fix'd that too. dlcs18
MyNameIsKooky
Rainbow Spirit Master
Posts: 9495
Joined: Mon Dec 01, 2008 10:18 pm
dlcs18 wrote:If you have 3 integers, named x, y, and z, and do this formula with it:
((x*y)/z)*((x*z)/y)*((y*z)/x), you will always get a whole number.
If you multiply the denominators with denominators and numerators with neumerators you'll get:
(x^2*y^2*z^2)/(xyz). Dividing those leaves you with xyz and thus it's not a fraction at all, so you'll always get whole numbers.

EDIT: Unless you plug in fractions. dlcs18
Rainbow MegaStar
Posts: 3282
Joined: Sun Jul 09, 2006 9:44 pm
Oh... How could I have not realised it was just producing x*y*z? I fail.
dlcs18
Blast!10
Rainbow Star
Posts: 1732
Joined: Thu Nov 02, 2006 7:26 pm
Location: Tel Aviv
^_^ wrote:I hate word "White".
Its annoying when you say that like 1000000000000 times.
Let's see, how much time will it take my computer to write the word "white" 1 trillion times?

This is the PHP code I used:

Code: Select all

``````<?

\$i=0;
\$myFile = "lol.txt";
\$fh = fopen&#40;\$myFile, 'a'&#41;;

\$Data = "white ";
while &#40;\$i < 1000000000000&#41; &#123;
fwrite&#40;\$fh, \$Data&#41;;
\$i++;
&#125;

fclose&#40;\$fh&#41;;

?>``````
Using that code, it took my computer one minute to write "white" 167,209 times (see this link). Dividing that by 60 makes 2,786.8166... which is roughly 2,787. This means my computer writes 2787 copies of the word "white" per second.
If I want to find out how many seconds my computer will spend writing "white" 1 trillion times I have to divide 1 trillion by 2,787. That makes roughly 358,808,755. 358,808,755 seconds = 5,980,146 minutes = 99,669 hours = 4,153 days = about 138 months = 11 years.

Nope, I'm not going to wait 11 years for my computer to do that.

Also, thanks to tyteen for helping me with the code.
Marinus
Rainbow AllStar
Posts: 4686
Joined: Sun Dec 16, 2007 2:20 pm
Blast!10 wrote:
^_^ wrote:Its annoying when you say that like 1000000000000 times.
Nope, I'm not going to wait 11 years for my computer to do that.
And then your computer has not even said the word, only written on the screen. Let's say a computer can say the word at most 4 times/second (while you still can understand it) it will take about 8000 years. Yes, I guess that will be pretty annoying.  LittleZbot
Rainbow MegaStar
Posts: 3036
Joined: Fri Jul 03, 2009 10:51 pm
Contact:

*sighs*

*runs off*

I hate Math.

*runs farther* To Shorty, who was immortalized in an adventure.
To Marinus, who was my community older brother.
To Janet, who I will remember every time I wear a toque.

May these Wonderlanders find more adventures in passing than they ever had in life.
Marinus
Rainbow AllStar
Posts: 4686
Joined: Sun Dec 16, 2007 2:20 pm
deleted
Last edited by Marinus on Fri Jul 16, 2010 12:07 am, edited 1 time in total. MyNameIsKooky
Rainbow Spirit Master
Posts: 9495
Joined: Mon Dec 01, 2008 10:18 pm
A few months ago, I thought up a nice formula for finding square numbers one at a time. Think about these square numbers...

1
4
9
16
25

Each number is 2n+1 after each other where n is the number's square root. Here's the formula applied in the space after.

1 +3 [1+2(1)+1=3, we add the answer to the original number to get the next square number, 4]
4 +5
9 +7
16 +9
25 +11
...

Thus, we can find that the next square number after 25 is 36, which has a square root of 6, and so on. Continuing the sequence using the formula to help...

36 +13
49 +15
64 +17
81 +19
100 +21
121 +23
144 +25
169 +27
Etc... Marinus
Rainbow AllStar
Posts: 4686
Joined: Sun Dec 16, 2007 2:20 pm
I think you're right Kooky, but I see an even easier pattern: Each next square is the previous square + the next odd number (not quite sure if odd is the right word but I mean a number not to be divided by 2 and still an integer): 1, 3, 5, 7, etc...

Edit: But I have to admit that yours is more Mathematical: (n+1)^2 = n^2 + 2n + 1 Nobody
Rainbow Spirit Chaser
Posts: 5513
Joined: Thu Aug 21, 2008 5:52 pm
BEEF!

What is it? i should change my signature to not be rude to pcpuzzle
MyNameIsKooky
Rainbow Spirit Master
Posts: 9495
Joined: Mon Dec 01, 2008 10:18 pm
BEEF = 48879 Marinus
Rainbow AllStar
Posts: 4686
Joined: Sun Dec 16, 2007 2:20 pm
I did not calculate it, but I guess it's hexathings.  mqdar
Rainbow Star
Posts: 1436
Joined: Mon May 09, 2005 10:46 pm
This isn't directly related to maths, but it makes no sense to me and I can't find any info about it with on the internet.

Have any of you ever opened WA level files in hex-editors? Some numbers are stored in a really strange way. Here's four different ones I've found:

c0 3f = 1
20 40 = 2
60 40 = 3
90 40 = 4

Double-digit hex values for storing simple numbers. Help please? [7:23:57 AM] 'a'a: *clicks here*
Marinus
Rainbow AllStar
Posts: 4686
Joined: Sun Dec 16, 2007 2:20 pm
Probably it doesn't make sense at all, but I found a pattern. If you write those numbers binary, you get this:

1100 0000 0011 1111
0010 0000 0100 0000
0110 0000 0100 0000
1001 0000 0100 0000

When you take only the 2nd to 9th bits (blue ones) and mirror them, you get 1, 10, 11 and 100, which is 1,2,3 and 4. The other bits (black ones) don't make any sense to me; maybe they are used for something else.

But maybe it's complete nonsense though.  MyNameIsKooky
Rainbow Spirit Master
Posts: 9495
Joined: Mon Dec 01, 2008 10:18 pm
The hex numbers are either pointlessly compressed or encrypted. But what Marinus said seems a lot more likely, and seems to point towards the fact that the hex numbers in the level files are encrypted.