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Geek Culture / Math problem

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Phaelax
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Posted: 6th Jan 2014 07:50 Edited at: 6th Jan 2014 07:54
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At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party?


I found that question on a website. I came up with
12 people
for my answer.

I thought it out on paper first, then thought of a simple program that can solve it.



I've been trying to think of a way to represent this solution mathematically and here's what I came up with. The summation of N equals 66.(I think I worded that correctly) But I'm not entirely sure how I would solve for N. I know it can be broken down into: n(n+1)/2 = 66



In this case, N should equal 11 and so therefore the answer to the problem would be the value of N plus 1.

http://zimnox.com

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Dark Java Dude 64
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Posted: 6th Jan 2014 08:35 Edited at: 6th Jan 2014 08:37
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Number of people in the group on the left, number of possible handshakes on the right:

02-01
03-03
04-06
05-10
06-15
07-21
08-28
09-36
10-45
11-55
12-66

Yep, you got that correct. I did the first few manually, and I noticed the second finite difference was one, and extrapolated from there.

This should be able to be modeled by a quadratic equation because of that, but right now I'm too lazy to find that.

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Hodgey
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Posted: 6th Jan 2014 08:43
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Another way to do this is by using combinations.

(n choose 2) = 66

n! / [ (n-2)! * 2! ] = 66

n!/ (n-2)! = 132

n*(n-1) = 132

Solve the quadratic and you get n = -11 or n = 12. Obviously, you take the positive one.
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Matty H
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Posted: 6th Jan 2014 11:13
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Quote: "Solve the quadratic and you get n = -11 or n = 12. Obviously, you take the positive one. "


But it is also good to know that if you could have negative people then you would need 11 of them to total 66 handshakes

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Libervurto
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Posted: 6th Jan 2014 16:58 Edited at: 6th Jan 2014 17:00
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I worked this out in the shower using the steamy door as a board.

h is handshakes, p is people:

h = (p2 - p) / 2

2h = p2 - p

I don't know if there is a better way to simplify in terms of p but I realised this meant the next square number up from 2h is p2. 2h = 132 so 144 is the next square, which is 12².

[off topic]
When did we stop saying "I know not." and change it to "I don't know."? I dislike this use of "do" as a generic verb, it's totally redundant. Why say "I do not know"? It sounds like, "I am doing the opposite of knowing!". Why does "I not know" sound illiterate while we are perfectly happy with "I do not know"? It's the same thing, just slipping in a generic verb before the not to trick us into thinking it's a properly formed sentence. Maybe we need a word like "dislike" for knowing, I disknow why no-one has thought of that.


Formerly OBese87.
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Phaelax
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Posted: 6th Jan 2014 20:10
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I've never heard anyone say 'I know not'. That sounds like Yoda speak

http://zimnox.com
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Libervurto
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Posted: 7th Jan 2014 02:41
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Quote: "I've never heard anyone say 'I know not'. That sounds like Yoda speak"

Neat 'aint it!

Interesting how the French negative is almost like using tags "Je ne comprends pas...", might as well be, "Je [not]comprends[/not]..."


Formerly OBese87.
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Kezzla
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Posted: 7th Jan 2014 04:42
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Libervurto wrote: "Maybe we need a word like "dislike" for knowing, I disknow why no-one has thought of that."


In Australian we do have such a word. I dunno why the rest of the world doesn't use it.

Ok, Jokes over, No more eye burn.
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Yodaman Jer
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Posted: 7th Jan 2014 04:50
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Quote: "But it is also good to know that if you could have negative people then you would need 11 of them to total 66 handshakes
"


Good thing I have -11 friends then!

@Phaelax:

"I know not" was used quite a long time ago, and practically nobody says it anymore. I say it sometimes, but I like to sound old-fashioned when I'm being social.

I know not why no one else ever uses the phrase.


Check me out on Twitter! Read my blog!
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Hodgey
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Posted: 7th Jan 2014 06:01
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Quote: "But it is also good to know that if you could have negative people then you would need 11 of them to total 66 handshakes"

Unfortunately, most of the negative people I know aren't warming to handshakes. Maybe that's why they're so negative, they need more handshakes in their life...about 66 of them.
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Dark Java Dude 64
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Posted: 7th Jan 2014 08:35
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Don't get the negative people too close to the positive people, or a current will flow.

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easter bunny
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Posted: 12th Jan 2014 23:50 Edited at: 12th Jan 2014 23:51
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Btw: There are two types of people, those who can extrapolate from incomplete data...


Audacia Games
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Kezzla
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Posted: 13th Jan 2014 08:57
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Quote: "Don't get the negative people too close to the positive people, or a current will flow."


People always used to say that I have a magnetic personality, too late did I realize they meant I was repulsive.

Ok, Jokes over, No more eye burn.
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BatVink
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Posted: 13th Jan 2014 21:16
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Quote: "I've never heard anyone say 'I know not'. That sounds like Yoda speak"


Almost every person married under the Christian rite has said it...

"I know not of any lawful impediment why I may not marry..."

Back on the original question, if there used to be 11 people in the room will 66 handshakes now take place, and if so how will we ever know it happened as the equation said it should?

ten-net consulting limited
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Green Gandalf
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Posted: 15th Jan 2014 01:02
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Quote: "When did we stop saying "I know not." and change it to "I don't know."? I dislike this use of "do" as a generic verb, it's totally redundant. Why say "I do not know"?"


That made me laugh.

Why did you say "When did we stop saying ..."?



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Neuro Fuzzy
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Posted: 15th Jan 2014 11:02
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Quote: "Why does "I not know" sound illiterate while we are perfectly happy with "I do not know"?"


I don't know.


"I <3 u 2 bbz" - Dark Frager
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BatVink
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Posted: 15th Jan 2014 11:39
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One reason may be because you need to differentiate between:

I do not - lack of...
I can not - Something preventing you from...
I will not - A decision not to...

If I remember my English lessons, it's called a modal verb. It sets the context in which you are replying in the negative.

And if you are an American, remember to ask not what your country can do for you...

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Phaelax
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Posted: 15th Jan 2014 19:24
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Or...

!(ask what your country can do for you...)

http://zimnox.com
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nonZero
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Posted: 15th Jan 2014 20:05
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Someone had to post this in this thread:

If you're having math problems, I feel bad for you, son
I got ninety-nine problems but a math ain't one

99 is 66 inverted which makes it funnier.

*drum roll #3 today* ...Aaaaand, I'm gonna go do something actually constructive now before I post something silly in every thread.

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BatVink
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Posted: 15th Jan 2014 21:45
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Quote: "but a math ain't one"


At the risk of sounding xenophobic, there is a joke in the UK about the US being bad with numbers because they haven't realised yet that there is more than one math. (We say maths as the full word is mathematics)

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Seditious
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Posted: 15th Jan 2014 22:08
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Wow, so xenophobic BatVink! I'm sure all Americans are deeply offended by your tasteless joke.

I am no good at mathematic so I can't help with the problem.
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Dark Java Dude 64
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Posted: 15th Jan 2014 23:08
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Between YouTube and these forums, I have picked up quite a bit of UK grammar and vocab over the past few years and now speak with it regularly. I say maths all the time, for instance.

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Libervurto
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Posted: 16th Jan 2014 13:34
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I have gone the other way and now think math is better. Mathematics is not plural, there is no such thing as a mathematic.


Formerly OBese87.
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Kezzla
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Posted: 16th Jan 2014 16:56
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if there were mathematics, I would love to meet their peers...
math = universe
as apposed to maths = universes
which sounds ridiculous.
however... as uneducated as I am regarding math,
Could there be maths in a modal sense?
which would be maths, singularly existing as a modal argument, but math also existing as a whole via unifying conceptualization.
Just like I have always argued that I am the universe, and also an individual existing within the confines of reality.
Math being a chain of logic... and existing as maths experienced as a modal parameter outlining a matrix of possibility...

Is there not room for math and maths to define each other through polar interpolation?...

damn, Drunk Kieran should not post on the interwebs... however... I still wonder. There will be no delete! Post! Post MOFO!
Drunk Kieran Wholeheartidly backs this post...
Sober Kieran is mortified and will apologize soon enough.
Drunk Kieran is curious enough, and is sure enough of having made a point to press send...

Let there be non-sense threaded with maybe's.

I am the bringer of the sandwiches!!!

Ok, Jokes over, No more eye burn.
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Kezzla
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Posted: 16th Jan 2014 17:10 Edited at: 16th Jan 2014 17:11
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Ok, Jokes over, No more eye burn.

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BatVink
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Posted: 16th Jan 2014 17:29
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Apparently it's derived from a greek word that meant "all things mathematical", hence there has never been a singular version of the full word. Just like Physics which is "all things physical".

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Seditious
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Posted: 16th Jan 2014 19:04
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BatVink beat me to it.

Anyway I'm off to study some physic.
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Phaelax
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Posted: 17th Jan 2014 03:04
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Huh?

http://zimnox.com
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nonZero
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Posted: 17th Jan 2014 12:41
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So, I turned this thread into Postcom (portmanteau of Posting Competition that would catch on better in Japan). Anyhoo, here in RSA we also use "maths" as the abbreviation. In fact we add -s to many things we shouldn't and omit -s from plenty too, ie:
"I can like to be wearing a jean-pant"
is derive from
"I am wearing jeans".
This is due to poor English-Afrikaans translation and cultural slang (there are 11 official languages and countless slang subsets). We're likely the only country with slang of slang.

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Green Gandalf
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Posted: 17th Jan 2014 18:12
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Just read the last few posts and realised I couldn't remember what the thread was about. Had to go back to the first post.



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nonZero
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Posted: 17th Jan 2014 23:43
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This thread is about points! ...Oh, wait, that's the other thread.

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