Page 1 of 3 123 LastLast
Results 1 to 30 of 86
  1. - Top - End - #1
    Troll in the Playground
     
    enderlord99's Avatar

    Join Date
    Jul 2011
    Location
    A film shoot.

    Default Completely pointless math facts

    If you have a timer that, for some reason, can be set for FF:DD:hh:mm:ss with no error checking, you can set it for up to 1368715689 seconds by using only nines. This is somewhere between 43 and 44 years, but I can't convert it to YY:MM:DD:hh:mm:ss time because Wolframalpha insists on rounding prematurely.
    Spoiler: Previous avatars
    Show
    Spoiler: Vanity quotes
    Show
    Quote Originally Posted by Strigon View Post
    Wow.
    That took a very sudden turn for the dark.

    I salute you.
    Quote Originally Posted by AuthorGirl View Post
    I wish it was possible to upvote here.

    I use braces (also known as "curly brackets") to indicate sarcasm.
    Explanation here.

  2. - Top - End - #2
    Titan in the Playground
     
    BlackDragon

    Join Date
    Feb 2007
    Location
    Manchester, UK
    Gender
    Male

    Default Re: Completely pointless math facts

    Um, what is FF here?

  3. - Top - End - #3
    Troll in the Playground
     
    enderlord99's Avatar

    Join Date
    Jul 2011
    Location
    A film shoot.

    Default Re: Completely pointless math facts

    Quote Originally Posted by factotum View Post
    Um, what is FF here?
    Fortnight Fortnight
    Spoiler: Previous avatars
    Show
    Spoiler: Vanity quotes
    Show
    Quote Originally Posted by Strigon View Post
    Wow.
    That took a very sudden turn for the dark.

    I salute you.
    Quote Originally Posted by AuthorGirl View Post
    I wish it was possible to upvote here.

    I use braces (also known as "curly brackets") to indicate sarcasm.
    Explanation here.

  4. - Top - End - #4
    Ogre in the Playground
     
    gomipile's Avatar

    Join Date
    Jul 2010

    Default Re: Completely pointless math facts

    Quote Originally Posted by enderlord99 View Post
    If you have a timer that, for some reason, can be set for FF:DD:hh:mm:ss with no error checking, you can set it for up to 1368715689 seconds by using only nines. This is somewhere between 43 and 44 years, but I can't convert it to YY:MM:DD:hh:mm:ss time because Wolframalpha insists on rounding prematurely.
    I don't know what standard you use for dividing out the months, but skipping months I get 43 years, 146 days, 14 hours, 48 minutes, and 9 seconds. That's if I use exactly 365 days per year with no leap days or leap seconds, though.
    Quote Originally Posted by Harnel View Post
    where is the atropal? and does it have a listed LA?

  5. - Top - End - #5
    Colossus in the Playground
     
    JNAProductions's Avatar

    Join Date
    Jul 2014
    Location
    Fighting Demons!

    Default Re: Completely pointless math facts

    Quote Originally Posted by enderlord99 View Post
    If you have a timer that, for some reason, can be set for FF:DD:hh:mm:ss with no error checking, you can set it for up to 1368715689 seconds by using only nines. This is somewhere between 43 and 44 years, but I can't convert it to YY:MM:DD:hh:mm:ss time because Wolframalpha insists on rounding prematurely.
    I appreciate this utterly useless fact. :P

    Unfortunately, I don't have any to share myself.
    I have a LOT of Homebrew!

    Current Avatar by Elder Tsofu, who is awesome!

    Spoiler: Former Avatars
    Show
    Spoiler: Avatar (Not In Use) By Professor Gnoll!
    Show


    Spoiler: Avatar (Not In Use) By Cdr. Fallout!
    Show

  6. - Top - End - #6
    Surgebinder in the Playground Moderator
     
    Douglas's Avatar

    Join Date
    Aug 2005
    Location
    Mountain View, CA
    Gender
    Male

    Default Re: Completely pointless math facts

    e𝜋-𝜋 is extremely close to 20. So close, in fact, that 6 of its first 7 digits past the decimal point are 9. And the one digit that isn't 9 is actually not at the end of those 7 - it's a 0 right in the middle instead.

    19.99909997919...
    Like 4X (aka Civilization-like) gaming? Know programming? Interested in game development? Take a look.

    Avatar by Ceika.

    Archives:
    Spoiler
    Show
    Saberhagen's Twelve Swords, some homebrew artifacts for 3.5 (please comment)
    Isstinen Tonche for ECL 74 playtesting.
    Team Solars: Powergaming beyond your wildest imagining, without infinite loops or epic. Yes, the DM asked for it.
    Arcane Swordsage: Making it actually work (homebrew)

  7. - Top - End - #7
    Ettin in the Playground
     
    Fyraltari's Avatar

    Join Date
    Aug 2017
    Location
    France
    Gender
    Male

    Default Re: Completely pointless math facts

    i to the power of i is a real number.
    "Any technology distinguishable from magic is insufficiently advanced."
    Gehm's corollary to Clarke's Third Law



    Forum Wisdom

  8. - Top - End - #8
    Ogre in the Playground
     
    truemane's Avatar

    Join Date
    Mar 2007
    Location
    London Below
    Gender
    Male

    Default Re: Completely pointless math facts

    There's a great SMBC comic about someone asking his partner to speak 'mathy' to him in a sexy way, that culminates with him declaring she's a "mathy, mathy girl" that's always made me laugh, and would be the perfect compliment to this thread.

    But it's JUST explicitly sexual enough that I don't want to link it.

    But, suffice it say, you're all mathy, mathy playgrounders.
    The Ties that Bind (Masks) / IC / OC
    Cosmic Agents (FASERIP) / IC / OC

    Pony Sherlock-atar by Dirtytabs. May her backups be never corrupted.

  9. - Top - End - #9
    Titan in the Playground
     
    Peelee's Avatar

    Join Date
    Dec 2009
    Location
    Birmingham, AL
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by truemane View Post
    There's a great SMBC comic about someone asking his partner to speak 'mathy' to him in a sexy way, that culminates with him declaring she's a "mathy, mathy girl" that's always made me laugh, and would be the perfect compliment to this thread.

    But it's JUST explicitly sexual enough that I don't want to link it.

    But, suffice it say, you're all mathy, mathy playgrounders.
    Funny, my first thought was the SMBC comic about math transactions that ended with the harmonic sequence.
    Cuthalion's avatars rock. Like this very fine dragon he made me.

  10. - Top - End - #10
    Ogre in the Playground
     
    Vizzerdrix's Avatar

    Join Date
    Aug 2009
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by enderlord99 View Post
    If you have a timer that, for some reason, can be set for FF:DD:hh:mm:ss with no error checking, you can set it for up to 1368715689 seconds by using only nines. This is somewhere between 43 and 44 years, but I can't convert it to YY:MM:DD:hh:mm:ss time because Wolframalpha insists on rounding prematurely.
    To be fair, no one likes a premature rounder.
    ,,,,^..^,,,,


    Quote Originally Posted by Haldir View Post
    Edit- I understand it now, Fighters are like a status symbol. If you're well off enough to own a living Fighter, you must be pretty well off!

  11. - Top - End - #11
    Titan in the Playground
     
    Grey_Wolf_c's Avatar

    Join Date
    Aug 2007

    Default Re: Completely pointless math facts

    Interested in MitD? Join us in MitD's thread.
    There is a world of imagination
    Deep in the corners of your mind
    Where reality is an intruder
    And myth and legend thrive
    Quote Originally Posted by woweedd View Post
    I would say that's the dumbest theory Grey Wolf's heard, but, let's be honest: It's Grey Wolf. They've probably heard dumber theories today. Point is, neat idea, but it's a real stretch.
    Ceterum autem censeo Hilgya malefica est

  12. - Top - End - #12
    Surgebinder in the Playground Moderator
     
    Douglas's Avatar

    Join Date
    Aug 2005
    Location
    Mountain View, CA
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Grey_Wolf_c View Post
    Except 2 and 3.
    Like 4X (aka Civilization-like) gaming? Know programming? Interested in game development? Take a look.

    Avatar by Ceika.

    Archives:
    Spoiler
    Show
    Saberhagen's Twelve Swords, some homebrew artifacts for 3.5 (please comment)
    Isstinen Tonche for ECL 74 playtesting.
    Team Solars: Powergaming beyond your wildest imagining, without infinite loops or epic. Yes, the DM asked for it.
    Arcane Swordsage: Making it actually work (homebrew)

  13. - Top - End - #13
    Titan in the Playground
     
    Peelee's Avatar

    Join Date
    Dec 2009
    Location
    Birmingham, AL
    Gender
    Male

    Default Re: Completely pointless math facts

    Oh, I'd forgotten about the 37 tricks for a long time.

    A.) any single digit number multiplied by 3, then by 37, will give a product of the original number three times. Eg (5)(3)(37)=555, or (9)(3)(37)=999. The double digits also kinda work this way but you dont want to read me describe it.

    2.) if you multiply by anything that gives a three-digit product, then move the first digit of the product to the back of the product, the resulting number is evenly divisible by 37. Eg (5)(37) = 185. 851/37 = 23, or (11)(37) = 407. 74/37 = 2. Or (15)(37) = 555. 555/37 = 15. If you want to be cheeky about it.
    Last edited by Peelee; 2019-03-31 at 10:34 PM.
    Cuthalion's avatars rock. Like this very fine dragon he made me.

  14. - Top - End - #14
    Titan in the Playground
     
    BlackDragon

    Join Date
    Feb 2007
    Location
    Manchester, UK
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Peelee View Post
    A.) any single digit number multiplied by 3, then by 37, will give a product of the original number three times. Eg (5)(3)(37)=555, or (9)(3)(37)=999.
    Er, yes, because multiplying by 3 and then 37 is the same as multiplying by 111? It would be rather more obvious if you just said any single digit number multiplied by 111 gives three times the original number.

  15. - Top - End - #15
    Titan in the Playground
     
    Kato's Avatar

    Join Date
    Apr 2008
    Location
    Germany
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Peelee View Post
    Oh, I'd forgotten about the 37 tricks for a long time.

    A.) any single digit number multiplied by 3, then by 37, will give a product of the original number three times. Eg (5)(3)(37)=555, or (9)(3)(37)=999. The double digits also kinda work this way but you dont want to read me describe it.

    2.) if you multiply by anything that gives a three-digit product, then move the first digit of the product to the back of the product, the resulting number is evenly divisible by 37. Eg (5)(37) = 185. 851/37 = 23, or (11)(37) = 407. 74/37 = 2. Or (15)(37) = 555. 555/37 = 15. If you want to be cheeky about it.
    The first factotum already debunked (explained) but the second is a neater trick. I'm curious if there is a way to prove it.. And why it only works for three digits but I can't answer off the top of my head.
    "What's done is done."

    Pony Avatar thanks to Elemental

  16. - Top - End - #16
    Ettin in the Playground
     
    Fyraltari's Avatar

    Join Date
    Aug 2017
    Location
    France
    Gender
    Male

    Default Re: Completely pointless math facts

    I've got it.

    So we have x = 37y where x is a three digit number, that means x = 100a + 10b + c where a, b and c are single digits (between 0 and 9 included).
    (in Peelee's first example, y = 5, x = 185, a = 1, b = 8 and c = 5)
    Moving the first digit to third position means creating a number z (851) where
    z = 100b + 10c + a = 10(x - 100a) + a (eliminating the hundreds, moving the dozens and units up and adding the new units)
    z = 10x - 1000a + a
    z = 10x - 999a (is 999 a multiple of 37? Yes 27*37 = 999)
    z = 10*37y - 27*37a
    z = 37(10y-27a)
    851 = 37(50-27) = 37*23

    So for this to work y must be greater (or equal to) 3 times a. (edit3 : since 10y-27a => 0 <=>y => 27/10 *a)

    EDIT:
    Quote Originally Posted by Grey_Wolf_c View Post
    Oooh, that's a nice one.

    EDIT the return:
    37*2 = 74, not a three digit number, 37*3 = 111 a three digit number, so for x to have three digits y must be between 3 and 27.

    EDIT the trilogy:
    37y = 100a + 10b + c
    y = (100/37)a + (10/37)b + (1/37)c
    100/37 = 2,7027... > 2 so in order for x to have three digits, y must be greater than 3 times a (3 included).

    There. Proved.

    I now await the easier, more beautiful proof.
    Last edited by Fyraltari; 2019-04-01 at 06:59 AM.
    "Any technology distinguishable from magic is insufficiently advanced."
    Gehm's corollary to Clarke's Third Law



    Forum Wisdom

  17. - Top - End - #17
    Titan in the Playground
     
    Peelee's Avatar

    Join Date
    Dec 2009
    Location
    Birmingham, AL
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by factotum View Post
    Er, yes, because multiplying by 3 and then 37 is the same as multiplying by 111? It would be rather more obvious if you just said any single digit number multiplied by 111 gives three times the original number.
    I am not a smart man. Also, I haven't looked at that since grade school, so blah.
    Quote Originally Posted by Fyraltari View Post
    I now await the easier, more beautiful proof.
    Spoiler: Wienersmith's got your back
    Show
    Cuthalion's avatars rock. Like this very fine dragon he made me.

  18. - Top - End - #18
    Ettin in the Playground
     
    Fyraltari's Avatar

    Join Date
    Aug 2017
    Location
    France
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Peelee View Post
    Spoiler: Wienersmith's got your back
    Show
    Spoiler: My years in math Classes Préparatoires in a nutshell
    Show
    "Any technology distinguishable from magic is insufficiently advanced."
    Gehm's corollary to Clarke's Third Law



    Forum Wisdom

  19. - Top - End - #19
    Titan in the Playground
     
    Kato's Avatar

    Join Date
    Apr 2008
    Location
    Germany
    Gender
    Male

    Default Re: Completely pointless math facts

    Ah, nicely done! I didn't think of substituting the 10b+c which is really stupid in hindsight.

    So the trick boils down to... 37 being a divisor of 999? Which means it should also work for only 3 (obviously), 9 (also) and 27 (less boring).
    I think I'll remember that trick, thanks!
    "What's done is done."

    Pony Avatar thanks to Elemental

  20. - Top - End - #20
    Ettin in the Playground
     
    Fyraltari's Avatar

    Join Date
    Aug 2017
    Location
    France
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Kato View Post
    Ah, nicely done! I didn't think of substituting the 10b+c which is really stupid in hindsight.
    Thank you! substituting 10b+c isn't actually needed as the important part is realizing that moving the first digit around means y = 10(x-100a) + a. I didn't streamline my reasoning before posting (as is evident by my multiple edits ) and I started with decomposing the numbers into multiples of ten which is always a good idea when there's digit manipulation (in base ten).

    Quote Originally Posted by Kato View Post
    So the trick boils down to... 37 being a divisor of 999? Which means it should also work for only 3 (obviously), 9 (also) and 27 (less boring).
    In order for it to work with 27, y needs to be greater than (or equal to) 3.7 times a (37/10 = 3.7) for every x in the hundreds.
    27y = 100a + u <=> y = (100/27)a + u/27
    100/27 = 3.70370... so it should work. Not sure about 9 and 3, though.

    Quote Originally Posted by Kato View Post
    I think I'll remember that trick, thanks!
    I probably will too.
    Last edited by Fyraltari; 2019-04-01 at 11:41 AM.
    "Any technology distinguishable from magic is insufficiently advanced."
    Gehm's corollary to Clarke's Third Law



    Forum Wisdom

  21. - Top - End - #21
    Ettin in the Playground
     
    Rockphed's Avatar

    Join Date
    Nov 2006
    Location
    Near Giant Graffiti.
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Fyraltari View Post
    i to the power of i is a real number.
    ... is it? The complex number is eiπ/2. So ii = ei^2π/2 = e-π/2.

    Okay, so it is.
    Quote Originally Posted by Wardog View Post
    Rockphed said it well.
    Quote Originally Posted by Yuki Akuma View Post
    We should change the collective noun for crocodiles to "an abundance of crocodiles".
    Dragontar by Serpentine.

    Now offering unsolicited advice.

  22. - Top - End - #22
    Troll in the Playground
     
    Griffon

    Join Date
    Jun 2013
    Location
    Bristol, UK

    Default Re: Completely pointless math facts

    Quote Originally Posted by Douglas View Post
    Except 2 and 3.
    Yes. These are primes. A pattern that doesn't include them is not a pattern for all primes.
    The end of what Son? The story? There is no end. There's just the point where the storytellers stop talking.

  23. - Top - End - #23
    Titan in the Playground
     
    Grey_Wolf_c's Avatar

    Join Date
    Aug 2007

    Default Re: Completely pointless math facts

    Quote Originally Posted by halfeye View Post
    Yes. These are primes. A pattern that doesn't include them is not a pattern for all primes.
    The actual mathematician in the video calls them subprimes. I'll take their word over yours, random internet person.

    Grey Wolf
    Interested in MitD? Join us in MitD's thread.
    There is a world of imagination
    Deep in the corners of your mind
    Where reality is an intruder
    And myth and legend thrive
    Quote Originally Posted by woweedd View Post
    I would say that's the dumbest theory Grey Wolf's heard, but, let's be honest: It's Grey Wolf. They've probably heard dumber theories today. Point is, neat idea, but it's a real stretch.
    Ceterum autem censeo Hilgya malefica est

  24. - Top - End - #24
    Troll in the Playground
     
    Griffon

    Join Date
    Jun 2013
    Location
    Bristol, UK

    Default Re: Completely pointless math facts

    Quote Originally Posted by Grey_Wolf_c View Post
    The actual mathematician in the video calls them subprimes. I'll take their word over yours, random internet person.

    Grey Wolf
    Yeah, I'm a random internet person, so is the person in the video. The definition of prime numbers is what it is, look it up sometime.
    The end of what Son? The story? There is no end. There's just the point where the storytellers stop talking.

  25. - Top - End - #25
    Titan in the Playground
     
    Peelee's Avatar

    Join Date
    Dec 2009
    Location
    Birmingham, AL
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Grey_Wolf_c View Post
    The actual mathematician in the video calls them subprimes. I'll take their word over yours, random internet person.

    Grey Wolf
    Counterpoint: it seems the mathematician in the video is defining primes based on the them having a value of one more than a multiple of 24 after being squared in addition to the other requirements. Which, after a few quick and dirty Google searches, does not seem to be a standardized definition at all.

    That said, I'm not a mathematician, and dude could be using a known definition I didn't uncover.
    Cuthalion's avatars rock. Like this very fine dragon he made me.

  26. - Top - End - #26
    Ettin in the Playground
     
    Fyraltari's Avatar

    Join Date
    Aug 2017
    Location
    France
    Gender
    Male

    Default Re: Completely pointless math facts

    A prime number by definition is an integer that is multiple of only two* integers 1 and itself. By that definition 2 and 3 are primes.

    1 has been excluded from the primes because it doesn't share the most useful properties of the other primes, most importantly that every integer can be written as a unique product of primes. So it was either getting 1 off the list or adding "except 1" to the primes' properties. I don't know of any reason not to consider 2 and 3 primes and I would like to hear that person's argument for it.
    "Any technology distinguishable from magic is insufficiently advanced."
    Gehm's corollary to Clarke's Third Law



    Forum Wisdom

  27. - Top - End - #27
    Titan in the Playground
    Join Date
    Dec 2009
    Gender
    Male2Female

    Default Re: Completely pointless math facts

    Quote Originally Posted by Grey_Wolf_c View Post
    The actual mathematician in the video calls them subprimes. I'll take their word over yours, random internet person.

    Grey Wolf
    I mean, it was a joke. Cause, like, subprime mortgages or whatever. The thing being proved was just that primes over three have this quality. Mathematicians do things like that sometimes, proving claims only with regard to almost all elements of a set, rather than all of them. The people in the video know that two and three are not prime.

  28. - Top - End - #28
    Titan in the Playground
     
    Peelee's Avatar

    Join Date
    Dec 2009
    Location
    Birmingham, AL
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by eggynack View Post
    The people in the video know that two and three are not prime.
    Cuthalion's avatars rock. Like this very fine dragon he made me.

  29. - Top - End - #29
    Barbarian in the Playground
     
    PaladinGuy

    Join Date
    Sep 2016

    Default Re: Completely pointless math facts

    Quote Originally Posted by eggynack View Post
    I mean, it was a joke. Cause, like, subprime mortgages or whatever. The thing being proved was just that primes over three have this quality. Mathematicians do things like that sometimes, proving claims only with regard to almost all elements of a set, rather than all of them. The people in the video know that two and three are not prime.
    Also the proof was actually (and explicitly) for all non-multiples of 2 and 3. But that would be boring and give away the trick.
    And from X being co-prime with 2 and co-prime with 3 to generally prime seems a nice way of doing it. You've only lost composites of higher primes, so 25, 35, 49... so for a region it nearly works both ways
    Spoiler: at 100 it's 23 primes to 7 composites
    Show
    by 1000 there are 166 primes out of 333 and by 5000 it's 667 out of 1666
    . But now you need weasel words for excluding 2&3) IIRC correctly 2 kind of gets this a fair bit, but it's so easy to say odd-prime, and of course odd, non three prime.gives away the pleading.


    Anyhow for my fact
    60*60*24*365 is within 1% of pi*107 or sqrt(10)*107. Allowing a moderate compromise between order of magnitude and accurate numbers for anything involving years.

  30. - Top - End - #30
    Titan in the Playground
     
    BlackDragon

    Join Date
    Feb 2007
    Location
    Manchester, UK
    Gender
    Male

    Default Re: Completely pointless math facts

    Quote Originally Posted by Rockphed View Post
    ... is it? The complex number is eiπ/2. So ii = ei^2π/2 = e-π/2.

    Okay, so it is.
    But all real numbers are just a sub-set of complex numbers anyway...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •