Bay 12 Games Forum

Please login or register.

Login with username, password and session length
Advanced search  
Pages: 1 ... 9968 9969 [9970] 9971 9972 ... 10973

Author Topic: Things that made you go "WTF?" today o_O  (Read 12997664 times)

JoshuaFH

  • Bay Watcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149535 on: January 14, 2020, 08:54:12 am »

I had literally never even heard of factorials until I freshened up on algebra on Brilliant.org. I'm just another in the long list of the American Educational System's victims.
Logged

Frumple

  • Bay Watcher
  • The Prettiest Kyuuki
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149536 on: January 14, 2020, 09:33:04 am »

I mean, it's not really a victimization thing? They're apparently not good for much outside of fairly specific applications most students won't encounter. That the system probably ignored it to poorly teach other crud might be, but not hammering in something that won't be used is just kinda'... there. Approaches a positive, even, really.
Logged
Ask not!
What your country can hump for you.
Ask!
What you can hump for your country.

Sanctume

  • Bay Watcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149537 on: January 14, 2020, 10:03:38 am »

Factorials, example 5! = 5 x 4 x 3 x 2 x 1.  It is part of Probability and Combinations chapter of my Algebra 2 (2nd semester) class in high school, and I think Linear Algebra in college (Computer Science major). 

I was more interested in the probability of a dice rolls in word problems, and I tend to relate them to playing games whether D&D or BattleTech board game.

Reelya

  • Bay Watcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149538 on: January 14, 2020, 06:53:30 pm »

How old is nature girl? She doesn't know factorials, so... Some twelve years old or less? I guess most countries go over that by that age.

Factorials are a weird thing. I think you either learn them early, or not at all. I learned them, but have no idea what they are used for. It's possible it went into something in calculus or differential equations that I've forgotten over the years.

They're use in probability a lot. For example, if you have 10 people, and you have to place then in some order, there are 10 possible people who could be first, but then you only have 9 people to pick from for second place, then 8 possible people for third place, and so on, so the number of ways to order N-things is N-factorial.

If you're only selecting a subset, say you're selecting 3 things out of 10, then the possible choices are 10*9*8, which can be written as 10!/7! or N!/(N-X)!, where N is how many things you have and X is how many things you're selecting.

But the above formula treats different orderings as unique. if you don't care about the order, then you can consider the number of ways that
the three things you pulled out of the bag can be ordered, and that's just 3! from the above explanation. So you can divide your 10*9*8 value by 3*2*1 to collapse alternate orderings.

So the formula for number of possible triplets (unordered) that can be selected from a bag of 10 things should be 10!/7!/3!, and the general formula is N!/( (N-K)! * K! ) for the number of possible selections of K things you can pull out of a bag of N things.
« Last Edit: January 14, 2020, 07:04:15 pm by Reelya »
Logged

bloop_bleep

  • Bay Watcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149539 on: January 14, 2020, 07:06:52 pm »

They'te used absolutely everywhere in combinatorics (edit: e.g. what Reelya was doing up there, but more complicated stuff too like graph theory). I'm frankly surprised you've gone through a computer science degree without encountering them much, as that should deal with at least some combinatorics if you learn data structures (again, e.g. graphs) or algorithms.

You should understand factorials are not a topic in themselves as far as I know, rather just an operation (like addition and multiplication) that comes up in some places.

They're also used in Taylor series from calculus, if you'll remember, and they come up by coincidence in some other areas.
« Last Edit: January 14, 2020, 07:08:45 pm by bloop_bleep »
Logged
Quote from: KittyTac
The closest thing Bay12 has to a flamewar is an argument over philosophy that slowly transitioned to an argument about quantum mechanics.
Quote from: thefriendlyhacker
The trick is to only make predictions semi-seriously.  That way, I don't have a 98% failure rate. I have a 98% sarcasm rate.

McTraveller

  • Bay Watcher
  • This text isn't very personal.
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149540 on: January 14, 2020, 08:30:17 pm »

What's really fun is 0! is (often) defined as 1.  And even more fun is the extension of factorials to more than just the natural numbers, the Gamma function. (Analytic continuation, yay!)  And there are lots of debates about how to define factorial of negative integers; Some say it's undefined (Gamma function, etc), some say it's the progressive product of the negative integers, some end up getting smaller and smaller (Roman factorial)
Logged

Egan_BW

  • Bay Watcher
  • Perhaps I'll
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149541 on: January 14, 2020, 08:43:44 pm »

Isn't it hilarious that people think we'll be able to communicate with extraterrestrials using math? ;P
Logged
Down at the bottom of the ocean. Beneath tons of brine which would crush you down. Not into broken and splintered flesh, but into thin soup. Into just more of the sea water. Where things live that aren't so different from you, but you will never live to touch them and they will never live to touch you.

Dunamisdeos

  • Bay Watcher
  • Duggin was the hero we needed.
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149542 on: January 14, 2020, 09:00:49 pm »

What's really fun is 0! is (often) defined as 1.  And even more fun is the extension of factorials to more than just the natural numbers, the Gamma function. (Analytic continuation, yay!)  And there are lots of debates about how to define factorial of negative integers; Some say it's undefined (Gamma function, etc), some say it's the progressive product of the negative integers, some end up getting smaller and smaller (Roman factorial)

If zero with an exclamation mark means one, I am simply going to scream ZERO like a madman at the top of my lungs the next time someone asks me say, how many burgers I want from the grill. This will make me a math jokester, the highest form of cerebral jokesmith there is.
Logged
FACT I: Post note art is best art.
FACT II: Dunamisdeos is a forum-certified wordsmith.
FACT III: "All life begins with Post-it notes and ends with Post-it notes. This is the truth! This is my belief!...At least for now."
FACT IV: SPEECHO THE TRUSTWORM IS YOUR FRIEND or BEHOLD: THE FRUIT ENGINE 3.0

JoshuaFH

  • Bay Watcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149543 on: January 14, 2020, 09:46:57 pm »

How old is nature girl? She doesn't know factorials, so... Some twelve years old or less? I guess most countries go over that by that age.

Factorials are a weird thing. I think you either learn them early, or not at all. I learned them, but have no idea what they are used for. It's possible it went into something in calculus or differential equations that I've forgotten over the years.

They're use in probability a lot. For example, if you have 10 people, and you have to place then in some order, there are 10 possible people who could be first, but then you only have 9 people to pick from for second place, then 8 possible people for third place, and so on, so the number of ways to order N-things is N-factorial.

If you're only selecting a subset, say you're selecting 3 things out of 10, then the possible choices are 10*9*8, which can be written as 10!/7! or N!/(N-X)!, where N is how many things you have and X is how many things you're selecting.

But the above formula treats different orderings as unique. if you don't care about the order, then you can consider the number of ways that
the three things you pulled out of the bag can be ordered, and that's just 3! from the above explanation. So you can divide your 10*9*8 value by 3*2*1 to collapse alternate orderings.

So the formula for number of possible triplets (unordered) that can be selected from a bag of 10 things should be 10!/7!/3!, and the general formula is N!/( (N-K)! * K! ) for the number of possible selections of K things you can pull out of a bag of N things.

Maybe this is what I've been looking for to answer the odd math questions I sometimes think about, like "If you have 10 pieces of gum, and only one of them is spearmint, and you pick one out randomly, how many times on average would you need to pick out a piece before you get the spearmint?"
Logged

Egan_BW

  • Bay Watcher
  • Perhaps I'll
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149544 on: January 14, 2020, 09:52:55 pm »

Conditional probability!
...I know that's called conditional probability, I don't know how it works. Sorry.
Logged
Down at the bottom of the ocean. Beneath tons of brine which would crush you down. Not into broken and splintered flesh, but into thin soup. Into just more of the sea water. Where things live that aren't so different from you, but you will never live to touch them and they will never live to touch you.

Eschar

  • Bay Watcher
  • hello
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149545 on: January 14, 2020, 11:00:42 pm »

I know if you have two independent events, and you want the probability of both happening at once, multiply the two probabilities (I think they have to both be decimals or fractions?) For the probability of either happening, add the probabilities. I don't know how to do dependent events.
Logged

WealthyRadish

  • Bay Watcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149546 on: January 14, 2020, 11:36:22 pm »

Maybe this is what I've been looking for to answer the odd math questions I sometimes think about, like "If you have 10 pieces of gum, and only one of them is spearmint, and you pick one out randomly, how many times on average would you need to pick out a piece before you get the spearmint?"

If you put the gum back before picking a new one:
https://en.wikipedia.org/wiki/Geometric_distribution

If you don't:
https://en.wikipedia.org/wiki/Hypergeometric_distribution
Logged

TamerVirus

  • Bay Watcher
  • Who cares
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149547 on: January 15, 2020, 05:17:26 pm »

Oh boy, we got bots again
Logged
What can mysteriously disappear can mysteriously reappear
*Shakes fist at TamerVirus*

Naturegirl1999

  • Bay Watcher
  • Thank you TamerVirus for the avatar switcher
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149548 on: January 15, 2020, 06:43:45 pm »

What bots? Humans can discuss probablilities without bots intervening
Logged

Egan_BW

  • Bay Watcher
  • Perhaps I'll
    • View Profile
Re: Things that made you go "WTF?" today o_O
« Reply #149549 on: January 15, 2020, 06:45:53 pm »

That's just something a die roller bot would say.
Logged
Down at the bottom of the ocean. Beneath tons of brine which would crush you down. Not into broken and splintered flesh, but into thin soup. Into just more of the sea water. Where things live that aren't so different from you, but you will never live to touch them and they will never live to touch you.
Pages: 1 ... 9968 9969 [9970] 9971 9972 ... 10973