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So, I screwed up the last math post of mine pretty badly, so I wish to redeem myself. But first I want to say something about why I love math so much.
I love math because I think it is the only "true" language, the one that doesn't have room for interpretations or misunderstanding (unless the reader is doing it wrong), and that it defines pretty much everything, except maybe emotions and stuff like that. And I like it because everything is so logical, maybe not if you don't understand it, but when you do everything is so obvious and you blame yourself for not seeing it before. Just my opinion 
(These questions are from my latest math test, they are not very hard/advanced, but I will go to the advanced math class next year so please, don't hate if you think the problems are easy)
1.
+ Show Spoiler +The value of a car decreases with 19.5% every year. The car's value in 2005 was 280 000NOK, it was a new car in 2003. a) Find the growth factor (I don't know if that is the correct english word for it) + Show Spoiler +b) What was the value of the car in 2007? + Show Spoiler +V(x)=280000*0.805^x
V(2)=280000*0.805^2
V(2)=181447~=180400NOK c) What did the car cost in 2003? + Show Spoiler +V(-2)=280000*0.805^-2
V(-2)=432082~=432100NOK
2.
+ Show Spoiler +Nadia and Tor(Thor is here!) are members of a movieclub. Nadia goes to 70% of the meetings, and independent of her, Tor goes to 60% of the same meetings. a) What's the chance of Nadia going to a meeting that Tor doesn't go to? + Show Spoiler +A=Nadia shows up, Tor doesn't.
P(A)=(1-P(Tor shows up))*P(Nadia shows up)
P(A)=(4/10)*(7/10)
P(A)=7/25=28% b) What is the probability of none going to the same a meeting? + Show Spoiler +B=None of them shows up
P(B)=(1-P(Tor shows up))*(1-P(Nadia shows up))
P(B)=(4/10)*(3/10)
P(B)=3/25=12% Three meetings were arranged in January c) What is the probability for Nadia going to all three meetings? + Show Spoiler +C=Nadia shows up at all three meetings
P(C)=(7/10)^3
P(C)=343/1000=34.3% d) What is the probability for both of them going to all three meetings? + Show Spoiler +D=Tor goes to all three meetings
P(D)=(6/10)^3
P(D)=27/125=21.6%
P(C union D)=P(C)*P(D)
P(C union D)=0.343*0.216
P(C union D)=0.074=7.4%
3.
+ Show Spoiler ++ Show Spoiler +The students at a school are arranging a christmas ball. The students rent a building and a local band that will play. The expenses are 10 000NOK, in addition there is food and drinks for the students which comes out at 120NOK per student. a) How much will the ball cost of 100 stundents come, and how much will it cost per student? + Show Spoiler +K(x)=10000+120x
K(100)=10000+120*100
K(100)=22000NOK b) We'll say that x amount of students attends, and we say that the combined expenses per student is E(x). Show that E(x)=10000/x+120 To cover the expenses, the ball-commitee sets the price tag on the tickets to 200NOK. c) How many students do the commitee count on? (That was horribly written) + Show Spoiler +Based on the graph I made on my calculator, they are hoping that at least 120 students buy a ticket. 200 students buy tickets, the commitee decides to give the extra money to charity. d) How much money is given to charity? + Show Spoiler +Total expenses=10000+120*200=34000NOK
Ticket income=200*200=40000NOK
Surplus=40000-34000=6000NOK
Answers added, hope this one was more enjoyable than the last one
Random fun question (Not math related)
+ Show Spoiler +What do you think this song is about? Lyrics (from tool's own website) + Show Spoiler +Die Eier von Satan
Eine halbe Tasse Staubzucker
Ein Viertel Teelöffel Salz
Eine Messerspitze türkisches Haschisch
Ein halbes Pfund Butter
Ein Teelöffel Vanillenzucker
Ein halbes Pfund Mehl
Einhundertfünfzig Gramm gemahlene Nüsse
Ein wenig extra Staubzucker ... und keine Eier
In eine Schüssel geben
Butter einrühren Gemahlene Nüsse zugeben und Den Teig verkneten
Augenballgroße Stücke vom Teig formen Im Staubzucker wälzen und Sagt die Zauberwörter
Simsalbimbamba Saladu Saladim
Auf ein gefettetes Backblech legen und Bei zweihundert Grad für fünfzehn Minuten backen und KEINE EIER
Bei zweihundert Grad für fünfzehn Minuten backen und Keine Eier .. Answer + Show Spoiler +
  
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I don't really think you should be using TL as a homework resource.
But for the heck of it, 2a. is 70%.
Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant. Therefore, Nadia's chances of going is still the established 70%.
Don't really feel like doing the others. Good luck.
EDIT: I don't know German...
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maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
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17018 Posts
I find it difficult to believe that this isn't a homework help thread.
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Aotearoa39261 Posts
On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
sin, cos and tan make perfect sense 
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On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
Whats hard to understand about the concepts?
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On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
What? Math is boring until you get to a certain level where you start to have questions that aren't intuitively obvious or routine arithmetic... You don't really have any idea what mathematics is if trig functions are something incomprehensible that must be learned as rote symbolic manipulation.
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^ I was just about to say that.
While I agree that at some point math gets... philosophical; sin, cos and tan is not it. Just go for physics major if you want to be able to relate your math to concrete problems.
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im pretty bad in math bbut here it goes..
+ Show Spoiler +1a. i dont understand this question
1b.181622.5
1c.399847
2a. 70
2b. 35%??
3a. 22000,220
3b.
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On February 01 2012 23:23 Empyrean wrote:
I find it difficult to believe that this isn't a homework help thread.
It was a math test we had, it has already been graded so even if it was a homework help thread it would be too late to do anything about it^^
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This isn't math this is arithmetic
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On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
I agree... like the axiom of choice and the Banach-Tarski paradox
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On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
Are you sure you know the basic operations of mathematics? Addition, subtraction, multiplication, division, and modular forms!
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On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
Sin, cos and tan are not illogical at all. They have an explanation/proof (IDK what th english word for this is), so IMO they are completely logical.
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On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic
That statement makes no sense to me, because if you use numbers to find other number I call it math.
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On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic
Arithmetic is a subset of math so... >.>
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On February 01 2012 23:47 Oracle wrote:Show nested quote +On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest I agree... like the axiom of choice and the Banach-Tarski paradox
What? Banach-Tarski is awesome
And you still have to understand the theory, it's just harder to.
EDIT: Arithmetic is math, just not very interesting math IMO. I completely disagree with what I quoted, because IMO, math doesn't get interesting until you have to investigate questions not doable by a computer.
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I found:
1 - 0,195 = 0.805 = 80,5%
2007 -> 225.400 - (225.400 x 0,195) = 181.447 NOK
2006 -> 280.000 - (280.000 x 0,195) = 225.400 NOK
2005 -> 280.000 NOK
2004 -> (280.000 x 0,195) + 280.000 = 334.600 NOK
2003 -> (334.600 x 0,195) + 334.600 = 399.847 NOK
1.a) 80,5%
1.b) 181.477 NOK
1.c) 399.847 NOK
What did I do wrong? oO
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OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first.
It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way.
You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question.
Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events.
If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .7 = .28.
Hope that helps
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On February 02 2012 00:20 fabiano wrote:
I found:
1 - 0,195 = 0.805 = 80,5%
2007 -> 225.400 - (225.400 x 0,195) = 181.447 NOK
2006 -> 280.000 - (280.000 x 0,195) = 225.400 NOK
2005 -> 280.000 NOK
2004 -> (280.000 x 0,195) + 280.000 = 334.600 NOK
2003 -> (334.600 x 0,195) + 334.600 = 399.847 NOK
1.a) 80,5%
1.b) 181.477 NOK
1.c) 399.847 NOK
What did I do wrong? oO
Switch the bolded ones with 0.805 and try again.
Also, 1a = 0.805, yes you could write it like you did, but it's not answering the question.
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On February 02 2012 00:24 DarkPlasmaBall wrote:OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first. It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way. You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question. Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events. If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .3 = .12. Hope that helps
Oops, I'm so bad at writing these kinds of questions in english, thanks for telling me
But the bolded part should be .7 because it's the probability of Nadia going is 70%=0.7, or am I being stupid now?
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On February 02 2012 00:03 achristes wrote:That statement makes no sense to me, because if you use numbers to find other number I call it math.
Mathematicians are constantly delving into supremely abstract realms to try to discover new theorems, corrollaries, etc. (mathematician's statements of truth) about extremely complicated situations. Some theorists work in areas that realistically may only be useful in practical ways to certain branches of physics. Mathematicians are creative thinkers, critical thinkers and problem solvers.
The OP is primarily concerned with questions of interpretation and execution of equations. Don't see the difference?
A problem for a mathematician goes something more like this:
The 'flea and comb space' is a topological space defined by a subspace of the two-dimensional coordinate plane which contains the point (0,1), all points (x,0), and all points (1/n,y), where n is any positive integer, and x and y are any real numbers between 0 and 1. Additionally, say that a point is "dense" (calling it "dense" because I actually don't remember the real term off hand) in the flea and comb set if it has points which are in the flea and comb set which are infinitely close to it, i.e. for any given arbitrarily small number, there is a point within that distance whcih is in the set. Prove that every point in this space is "dense" in the space, but that it is not the case that every point which is "dense" in the set is necessarily in the set.
The above is a relatively simple and straightforward math problem. More complicated problems may require a day or more of thought and reflection, experimentation and failure to resolve. This is the reason mathematicians bristle at the idea that saying 70% of $50 is $35 is "math" in the same sense. Math requires much more thought and effort.
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On February 02 2012 00:31 achristes wrote:Show nested quote +On February 02 2012 00:24 DarkPlasmaBall wrote:OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first. It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way. You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question. Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events. If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .3 = .12. Hope that helps Oops, I'm so bad at writing these kinds of questions in english, thanks for telling me But the bolded part should be .7 because it's the probability of Nadia going is 70%=0.7, or am I being stupid now?
I messed up the ending part to my previous post (should be ".4 * .7 = .28.") Edited it ^^
.4 = 1-.6 is P(Tor not going)
.7 is P(Nadia going)
If it were worded differently.
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On February 02 2012 00:31 Treehead wrote:Show nested quote +On February 02 2012 00:03 achristes wrote:On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic That statement makes no sense to me, because if you use numbers to find other number I call it math. Mathematicians are constantly delving into supremely abstract realms to try to discover new theorems, corrollaries, etc. (mathematician's statements of truth) about extremely complicated situations. Some theorists work in areas that realistically may only be useful in practical ways to certain branches of physics. Mathematicians are creative thinkers, critical thinkers and problem solvers. The OP is primarily concerned with questions of interpretation and execution of equations. Don't see the difference? A problem for a mathematician goes something more like this: The 'flea and comb space' is a topological space defined by a subspace of the two-dimensional coordinate plane which contains the point (0,1), all points (x,0), and all points (1/n,y), where n is any positive integer, and x and y are any real numbers between 0 and 1. Additionally, say that a point is "dense" (calling it "dense" because I actually don't remember the real term off hand) in the flea and comb set if it has points which are in the flea and comb set which are infinitely close to it, i.e. for any given arbitrarily small number, there is a point within that distance whcih is in the set. Prove that every point in this space is "dense" in the space, but that it is not the case that every point which is "dense" in the set is necessarily in the set. The above is a relatively simple and straightforward math problem. More complicated problems may require a day or more of thought and reflection, experimentation and failure to resolve. This is the reason mathematicians bristle at the idea that saying 70% of $50 is $35 is "math" in the same sense. Math requires much more thought and effort.
So what you are saying is that mathematicians don't like that "normal" people say that the simpler parts of math is math?
I can understand it if that is the case though, but what am I supposed to call it then? ^^
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On February 02 2012 00:33 DarkPlasmaBall wrote:Show nested quote +On February 02 2012 00:31 achristes wrote:On February 02 2012 00:24 DarkPlasmaBall wrote:OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first. It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way. You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question. Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events. If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .3 = .12. Hope that helps Oops, I'm so bad at writing these kinds of questions in english, thanks for telling me But the bolded part should be .7 because it's the probability of Nadia going is 70%=0.7, or am I being stupid now? I messed up the ending part to my previous post (should be ".4 * .7 = .28.") Edited it ^^ .4 for 1-.6 P(Tor not going) .7 for P(Nadia going) If it were worded differently.
It is now, mind checking for mistakes? ^^
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nvm. Going to read the blog. You people confuse me .
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On February 01 2012 23:25 Plexa wrote:Show nested quote +On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest sin, cos and tan make perfect sense
Never wondered by those three are actually doing what they were meant to do?
(giving the ratio in a triangle with one 90° angle)
Well, back then, I did not. But now I am wondering why that question never came into my mind.
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On February 02 2012 00:36 achristes wrote:Show nested quote +On February 02 2012 00:33 DarkPlasmaBall wrote:On February 02 2012 00:31 achristes wrote:On February 02 2012 00:24 DarkPlasmaBall wrote:OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first. It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way. You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question. Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events. If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .3 = .12. Hope that helps Oops, I'm so bad at writing these kinds of questions in english, thanks for telling me But the bolded part should be .7 because it's the probability of Nadia going is 70%=0.7, or am I being stupid now? I messed up the ending part to my previous post (should be ".4 * .7 = .28.") Edited it ^^ .4 for 1-.6 P(Tor not going) .7 for P(Nadia going) If it were worded differently. It is now, mind checking for mistakes? ^^
If you want your answer to 2a to be correct (with the same explanation that you have written in your OP), I would recommend changing the question from
"If Tor doesn't go to one of the meetings, what is the probability of Nadia going to the same meeting?"
to
"What's the chance of Nadia going to a meeting that Tor doesn't go to?"
This explicitly shows that you need to multiply the probability that Tor doesn't go to a meeting with the probability that Nadia does go
Otherwise, it'll stay at 70% for the reasons explained before.
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On February 02 2012 00:43 DarkPlasmaBall wrote:Show nested quote +On February 02 2012 00:36 achristes wrote:On February 02 2012 00:33 DarkPlasmaBall wrote:On February 02 2012 00:31 achristes wrote:On February 02 2012 00:24 DarkPlasmaBall wrote:OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first. It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way. You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question. Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events. If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .3 = .12. Hope that helps Oops, I'm so bad at writing these kinds of questions in english, thanks for telling me But the bolded part should be .7 because it's the probability of Nadia going is 70%=0.7, or am I being stupid now? I messed up the ending part to my previous post (should be ".4 * .7 = .28.") Edited it ^^ .4 for 1-.6 P(Tor not going) .7 for P(Nadia going) If it were worded differently. It is now, mind checking for mistakes? ^^ If you want your answer to 2a to be correct (with the same explanation that you have written in your OP), I would recommend changing the question from "If Tor doesn't go to one of the meetings, what is the probability of Nadia going to the same meeting?" to "What's the chance of Nadia going to a meeting that Tor doesn't go to?" This explicitly shows that you need to multiply the probability that Tor doesn't go to a meeting with the probability that Nadia does go Otherwise, it'll stay at 70% for the reasons explained before.
Thank you, I will PM you if I decide to make another one
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On February 02 2012 00:36 achristes wrote:Show nested quote +On February 02 2012 00:31 Treehead wrote:On February 02 2012 00:03 achristes wrote:On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic That statement makes no sense to me, because if you use numbers to find other number I call it math. Mathematicians are constantly delving into supremely abstract realms to try to discover new theorems, corrollaries, etc. (mathematician's statements of truth) about extremely complicated situations. Some theorists work in areas that realistically may only be useful in practical ways to certain branches of physics. Mathematicians are creative thinkers, critical thinkers and problem solvers. The OP is primarily concerned with questions of interpretation and execution of equations. Don't see the difference? A problem for a mathematician goes something more like this: The 'flea and comb space' is a topological space defined by a subspace of the two-dimensional coordinate plane which contains the point (0,1), all points (x,0), and all points (1/n,y), where n is any positive integer, and x and y are any real numbers between 0 and 1. Additionally, say that a point is "dense" (calling it "dense" because I actually don't remember the real term off hand) in the flea and comb set if it has points which are in the flea and comb set which are infinitely close to it, i.e. for any given arbitrarily small number, there is a point within that distance whcih is in the set. Prove that every point in this space is "dense" in the space, but that it is not the case that every point which is "dense" in the set is necessarily in the set. The above is a relatively simple and straightforward math problem. More complicated problems may require a day or more of thought and reflection, experimentation and failure to resolve. This is the reason mathematicians bristle at the idea that saying 70% of $50 is $35 is "math" in the same sense. Math requires much more thought and effort. So what you are saying is that mathematicians don't like that "normal" people say that the simpler parts of math is math? I can understand it if that is the case though, but what am I supposed to call it then? ^^
That's why Caller's saying that it's arithmetic, not math.
@Treehead: I think the word you want is limit point?
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On February 02 2012 00:45 achristes wrote:Show nested quote +On February 02 2012 00:43 DarkPlasmaBall wrote:On February 02 2012 00:36 achristes wrote:On February 02 2012 00:33 DarkPlasmaBall wrote:On February 02 2012 00:31 achristes wrote:On February 02 2012 00:24 DarkPlasmaBall wrote:OP, your 2a is wrong as I explained before. Conditional probability doesn't work in that way because the two events are independent. The second event isn't conditioned on the first. It's like saying, "I have a six-sided die and a coin. If I roll a 4 first, what's the chance of me flipping heads?" It's still 1/2. It doesn't change just because you roll the die in a certain way. You didn't ask what the chance of Tor not going to a meeting *and* Nadia going to meeting is simultaneously (in that case, you would carry out the calculation the same way you did). The wording (particularly the "If") makes it a different question. Nadia's probability of going to a meeting is independent of Tor, so whether or not Tor goes is irrelevant when deciding if Nadia goes. Therefore, Nadia's chances of going is still the established 70%. You don't need to include Tor's chance of not going, because- as was explicitly written in the instructions- the two events (Tor going and Nadia going) are independent events. If it was slightly reworded as "What's the chance of Tor not going *and* Nadia going to the same meeting", then it would be .4 * .3 = .12. Hope that helps Oops, I'm so bad at writing these kinds of questions in english, thanks for telling me But the bolded part should be .7 because it's the probability of Nadia going is 70%=0.7, or am I being stupid now? I messed up the ending part to my previous post (should be ".4 * .7 = .28.") Edited it ^^ .4 for 1-.6 P(Tor not going) .7 for P(Nadia going) If it were worded differently. It is now, mind checking for mistakes? ^^ If you want your answer to 2a to be correct (with the same explanation that you have written in your OP), I would recommend changing the question from "If Tor doesn't go to one of the meetings, what is the probability of Nadia going to the same meeting?" to "What's the chance of Nadia going to a meeting that Tor doesn't go to?" This explicitly shows that you need to multiply the probability that Tor doesn't go to a meeting with the probability that Nadia does go Otherwise, it'll stay at 70% for the reasons explained before. Thank you, I will PM you if I decide to make another one
Glad I could help The other ones look worded correctly ^^
EDIT: I haven't checked any other answers though.
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2d seems wrong to me. You probably didnt fill in the complete answer or something.
Both going to 3 consecutive meeting would be
(0,6*0,7) ^ 3 = 7,4%
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On February 02 2012 00:36 achristes wrote:Show nested quote +On February 02 2012 00:31 Treehead wrote:On February 02 2012 00:03 achristes wrote:On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic That statement makes no sense to me, because if you use numbers to find other number I call it math. Mathematicians are constantly delving into supremely abstract realms to try to discover new theorems, corrollaries, etc. (mathematician's statements of truth) about extremely complicated situations. Some theorists work in areas that realistically may only be useful in practical ways to certain branches of physics. Mathematicians are creative thinkers, critical thinkers and problem solvers. The OP is primarily concerned with questions of interpretation and execution of equations. Don't see the difference? A problem for a mathematician goes something more like this: The 'flea and comb space' is a topological space defined by a subspace of the two-dimensional coordinate plane which contains the point (0,1), all points (x,0), and all points (1/n,y), where n is any positive integer, and x and y are any real numbers between 0 and 1. Additionally, say that a point is "dense" (calling it "dense" because I actually don't remember the real term off hand) in the flea and comb set if it has points which are in the flea and comb set which are infinitely close to it, i.e. for any given arbitrarily small number, there is a point within that distance whcih is in the set. Prove that every point in this space is "dense" in the space, but that it is not the case that every point which is "dense" in the set is necessarily in the set. The above is a relatively simple and straightforward math problem. More complicated problems may require a day or more of thought and reflection, experimentation and failure to resolve. This is the reason mathematicians bristle at the idea that saying 70% of $50 is $35 is "math" in the same sense. Math requires much more thought and effort. So what you are saying is that mathematicians don't like that "normal" people say that the simpler parts of math is math? I can understand it if that is the case though, but what am I supposed to call it then? ^^
No. What he's saying is that mathematicians know what math is, and most people think that what they learned in high school is basically all there is to mathematics, with some additional complexity tacked on.
Addition and division and calculus and all the other parts of math that are routine calculations are lumped together as arithmetic because they are to math as paint-by-numbers is to watercolor painting. Sure, it's the same thing in a technical sense -- you have some brushes, and some water, and some paint, and you put paint and water on the brushes and make parts of the paper turn different colors, but it's not the same thing in a meaningful sense, as one is Art and the other is decidely not. THAT'S what people mean when they say that something which is clearly a mathematical statement or problem is "not real math". The beginnings of math is just about calculating some quantity. That's what people mean by arithmetic. The rest of math bears some resemblance to arithmetic, in that it involves formal symbolic manipulations to draw conclusions about the properties of certain abstract objects based on properties of other related objects, but that's about as far as the resemblance goes. (Unless you're in applied math, in which case I'm not talking to you).
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3c is also wrong.
10.000 + 120 * x = 200 * x (x = the amount of attendees)
x = 50 + 0,6 x
0,4 x = 50
x = 125
So the answer is 125 students
EDIT: I am going home now, I might check the other ones when I get home .
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Korea (South)497 Posts
On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
..... math is always pure logic. If you're getting to a point where math seems illogical, that means you don't have a logical understanding of the concepts.
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On February 02 2012 00:49 Koshi wrote:
2d seems wrong to me. You probably didnt fill in the complete answer or something.
Both going to 3 consecutive meeting would be
(0,6*0,7) ^ 3 = 7,4%
I agree with this.
P(Nadia going) * P(Tor going) = P(Nadia and Tor going to the same)
to the third power, for three meetings.
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On February 02 2012 01:03 DarkPlasmaBall wrote:Show nested quote +On February 02 2012 00:49 Koshi wrote:
2d seems wrong to me. You probably didnt fill in the complete answer or something.
Both going to 3 consecutive meeting would be
(0,6*0,7) ^ 3 = 7,4% I agree with this. P(Nadia going) * P(Tor going) = P(Nadia and Tor going to the same) to the third power, for three meetings.
Sorry, my bad.
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On February 02 2012 01:06 achristes wrote:Show nested quote +On February 02 2012 01:03 DarkPlasmaBall wrote:On February 02 2012 00:49 Koshi wrote:
2d seems wrong to me. You probably didnt fill in the complete answer or something.
Both going to 3 consecutive meeting would be
(0,6*0,7) ^ 3 = 7,4% I agree with this. P(Nadia going) * P(Tor going) = P(Nadia and Tor going to the same) to the third power, for three meetings. Sorry, my bad.
No worries. Are these questions you got wrong on a test? Or questions you got correct but just mis-translated into English? Or something else? Your OP says they were on your last math test, so are you looking to see if you got the answers right? Or are testing us?
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On February 02 2012 00:36 achristes wrote:Show nested quote +On February 02 2012 00:31 Treehead wrote:On February 02 2012 00:03 achristes wrote:On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic That statement makes no sense to me, because if you use numbers to find other number I call it math. Mathematicians are constantly delving into supremely abstract realms to try to discover new theorems, corrollaries, etc. (mathematician's statements of truth) about extremely complicated situations. Some theorists work in areas that realistically may only be useful in practical ways to certain branches of physics. Mathematicians are creative thinkers, critical thinkers and problem solvers. The OP is primarily concerned with questions of interpretation and execution of equations. Don't see the difference? A problem for a mathematician goes something more like this: The 'flea and comb space' is a topological space defined by a subspace of the two-dimensional coordinate plane which contains the point (0,1), all points (x,0), and all points (1/n,y), where n is any positive integer, and x and y are any real numbers between 0 and 1. Additionally, say that a point is "dense" (calling it "dense" because I actually don't remember the real term off hand) in the flea and comb set if it has points which are in the flea and comb set which are infinitely close to it, i.e. for any given arbitrarily small number, there is a point within that distance whcih is in the set. Prove that every point in this space is "dense" in the space, but that it is not the case that every point which is "dense" in the set is necessarily in the set. The above is a relatively simple and straightforward math problem. More complicated problems may require a day or more of thought and reflection, experimentation and failure to resolve. This is the reason mathematicians bristle at the idea that saying 70% of $50 is $35 is "math" in the same sense. Math requires much more thought and effort. So what you are saying is that mathematicians don't like that "normal" people say that the simpler parts of math is math? I can understand it if that is the case though, but what am I supposed to call it then? ^^
Let me put it in SC2 terms. Let's say I have a simulator which I have programmed to simulate an SC2 game for one player with clear goals in mind - the computer makes building choices based on a priority list I determined for it before the game. We assume a certain rush distance and a few other assumptions, but there's no map, no micro and the units just kind of attack each other simulatedly when the decision to attack comes up.
I wrote the priority list. I told it what it would need to attack. The units are SC2 units. Am I playing SC2? I could say that I'm playing SC2 but making it easier, but you'd tell me I missed the point of the game completely (I hope).
Math is about being creative, then being critical, then putting your work out on paper, the last step of which is the easiest, and the only one involved in arithmetic - that you write the numbers on the paper in the right order and remember how they go together. Nothing is being created, nothing is being critiqued, nothing is being improvised - it's rote. Math is far from being rote.
On February 02 2012 00:46 Nehsb wrote:Show nested quote +On February 02 2012 00:36 achristes wrote:On February 02 2012 00:31 Treehead wrote:On February 02 2012 00:03 achristes wrote:On February 01 2012 23:39 Caller wrote:
This isn't math this is arithmetic That statement makes no sense to me, because if you use numbers to find other number I call it math. Mathematicians are constantly delving into supremely abstract realms to try to discover new theorems, corrollaries, etc. (mathematician's statements of truth) about extremely complicated situations. Some theorists work in areas that realistically may only be useful in practical ways to certain branches of physics. Mathematicians are creative thinkers, critical thinkers and problem solvers. The OP is primarily concerned with questions of interpretation and execution of equations. Don't see the difference? A problem for a mathematician goes something more like this: The 'flea and comb space' is a topological space defined by a subspace of the two-dimensional coordinate plane which contains the point (0,1), all points (x,0), and all points (1/n,y), where n is any positive integer, and x and y are any real numbers between 0 and 1. Additionally, say that a point is "dense" (calling it "dense" because I actually don't remember the real term off hand) in the flea and comb set if it has points which are in the flea and comb set which are infinitely close to it, i.e. for any given arbitrarily small number, there is a point within that distance whcih is in the set. Prove that every point in this space is "dense" in the space, but that it is not the case that every point which is "dense" in the set is necessarily in the set. The above is a relatively simple and straightforward math problem. More complicated problems may require a day or more of thought and reflection, experimentation and failure to resolve. This is the reason mathematicians bristle at the idea that saying 70% of $50 is $35 is "math" in the same sense. Math requires much more thought and effort. So what you are saying is that mathematicians don't like that "normal" people say that the simpler parts of math is math? I can understand it if that is the case though, but what am I supposed to call it then? ^^ That's why Caller's saying that it's arithmetic, not math. @Treehead: I think the word you want is limit point?
Yeah, I tried to google "sequence of points approaching" and it gave me "limit", but somehow I thought there was another word for it in topology. Like a set which is closed contains its'... "boundary"? Maybe that's the right word. Idk - it's been at least 5 years since I did topology, and honestly I'm not sure why that's the problem that came to mind when I picked one out of my graduate career.
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On February 02 2012 01:09 DarkPlasmaBall wrote:Show nested quote +On February 02 2012 01:06 achristes wrote:On February 02 2012 01:03 DarkPlasmaBall wrote:On February 02 2012 00:49 Koshi wrote:
2d seems wrong to me. You probably didnt fill in the complete answer or something.
Both going to 3 consecutive meeting would be
(0,6*0,7) ^ 3 = 7,4% I agree with this. P(Nadia going) * P(Tor going) = P(Nadia and Tor going to the same) to the third power, for three meetings. Sorry, my bad. No worries. Are these questions you got wrong on a test? Or questions you got correct but just mis-translated into English? Or something else? Your OP says they were on your last math test, so are you looking to see if you got the answers right? Or are testing us?
I just thought it would be fun to share them, I got all of these questions right, but I forgot to add the last part of 2d and I mistranslated 2a
Don't forget about the random fun one, it is actually kind of funny, or maybe I just have a weird sense of humour ^^
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On February 02 2012 01:16 achristes wrote:Show nested quote +On February 02 2012 01:09 DarkPlasmaBall wrote:On February 02 2012 01:06 achristes wrote:On February 02 2012 01:03 DarkPlasmaBall wrote:On February 02 2012 00:49 Koshi wrote:
2d seems wrong to me. You probably didnt fill in the complete answer or something.
Both going to 3 consecutive meeting would be
(0,6*0,7) ^ 3 = 7,4% I agree with this. P(Nadia going) * P(Tor going) = P(Nadia and Tor going to the same) to the third power, for three meetings. Sorry, my bad. No worries. Are these questions you got wrong on a test? Or questions you got correct but just mis-translated into English? Or something else? Your OP says they were on your last math test, so are you looking to see if you got the answers right? Or are testing us? I just thought it would be fun to share them, I got all of these questions right, but I forgot to add the last part of 2d and I mistranslated 2a Don't forget about the random fun one, it is actually kind of funny, or maybe I just have a weird sense of humour ^^
I can't read German, but I saw the words Satan and Butter in the lyrics lol.
I read the spoilers too ^^
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Well, I always loved math, because its a mental thingy, but makes perfect sense, not like languages...
So my math, physics, chemistry and informatics tests are A and my latin and german tests are D :/
(English is B,its just better than german :D)
BTW, I am a native german speaker, here is a translation to english(broken english ofc  ):
+ Show Spoiler +The Eggs of Satan A half cup of sugar A quarter of a tea spoon of salt A knife point of turkish hashish A half pound of butter A tea spoon of vanilla sugar A half pound of flour 150 grams of milled nuts A bit more sugar and no eggs Put it into a bowl Add the Butter and the milled nuts and knead the dough Make balls as big as a eye out of the dough and toss them into the sugar, speak the magic words Simsalbimbamba Saladu Saladim (no explanation cuz... you know ) Put them onto a buttered baking plate and bake them at 200°C for 15 minutes and NO EGGS Bake them at 200°C for 15 minutes and NO EGGS
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On February 02 2012 00:57 Koshi wrote:3c is also wrong. 10.000 + 120 * x = 200 * x (x = the amount of attendees) x = 50 + 0,6 x 0,4 x = 50 x = 125 So the answer is 125 students EDIT: I am going home now, I might check the other ones when I get home .
Any feedback on this?
10.000 + 120 * x = cost of the project where x is the number of attendees.
200 * x = Profit of the project where x is the number of attendees.
10.000 + 120 * x = 200 * x (Cost = profit)
x = 125
Making a graph on your calculator and guessing the answer on your test with give you a 0/10 in Belgium .
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On February 02 2012 02:06 Koshi wrote:Show nested quote +On February 02 2012 00:57 Koshi wrote:3c is also wrong. 10.000 + 120 * x = 200 * x (x = the amount of attendees) x = 50 + 0,6 x 0,4 x = 50 x = 125 So the answer is 125 students EDIT: I am going home now, I might check the other ones when I get home . Any feedback on this? 10.000 + 120 * x = cost of the project where x is the number of attendees. 200 * x = Profit of the project where x is the number of attendees. 10.000 + 120 * x = 200 * x (Cost = profit) x = 125 Making a graph on your calculator and guessing the answer on your test with give you a 0/10 in Belgium .
They told us to use digital assets, and this is the answer I got. And FYI I didn't "guess" as you so blatantly put it, I used the function on my calc that shows what the x-value is when y=200. Why the answer is wrong I have no idea.
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On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest
In electrical engineering we learn that trigonometry relates real and imaginary numbers.
![[image loading]](http://agutie.homestead.com/files/e_i_pi_full.jpg)
Years later, I still don't quite understand. I mean, I can apply it, but I don't really GET IT.
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On February 02 2012 04:42 Uranium wrote:Show nested quote +On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest In electrical engineering we learn that trigonometry relates real and imaginary numbers. Years later, I still don't quite understand. I mean, I can apply it, but I don't really GET IT.
Well, if you think of e^x as just "a function f satisfying f' = f and sin x as a solution to f'' = -f, then it's natural to think that there's possibly a way to build e^x out of sinx and cosx.
So you see if it's possible to find numbers a,b,c,d such that e^x = a*sin(cx) + b*cos(cx). Then, plugging in x = 0, we get b = 1, and taking derivatives, we get -bc = a and ac = b, or ac = 1 and -c = a, which then gets us a^2 = -1. So this brings a connection with imaginary numbers, and a = i and c = -i. And we get e^x = isin(-ix)+cos(-ix). You can check that it satisfies f' = f, and if you want this to be rigorous you can prove theorems about what the possible values of f are given that and some more information. If we plug in x = i*y, we get e^iy = cos(y)+isin(y).
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On February 02 2012 05:11 Nehsb wrote:Show nested quote +On February 02 2012 04:42 Uranium wrote:On February 01 2012 23:21 ETisME wrote:
maths is fun until you get to a certain level where you starts to have questions that would get illogical (or basically you are required to abandon understanding the theory and learn to just DO maths), first one in my mind was sin, cos and tan.
If you like these kind of maths, stats are more to your taste to be honest In electrical engineering we learn that trigonometry relates real and imaginary numbers. Years later, I still don't quite understand. I mean, I can apply it, but I don't really GET IT. Well, if you think of e^x as just "a function f satisfying f' = f and sin x as a solution to f'' = -f, then it's natural to think that there's possibly a way to build e^x out of sinx and cosx. So you see if it's possible to find numbers a,b,c,d such that e^x = a*sin(cx) + b*cos(cx). Then, plugging in x = 0, we get b = 1, and taking derivatives, we get -bc = a and ac = b, or ac = 1 and -c = a, which then gets us a^2 = -1. So this brings a connection with imaginary numbers, and a = i and c = -i. And we get e^x = isin(-ix)+cos(-ix). You can check that it satisfies f' = f, and if you want this to be rigorous you can prove theorems about what the possible values of f are given that and some more information. If we plug in x = i*y, we get e^iy = cos(y)+isin(y).
If someone is interested in this he should look for Euler's formula (and how he got there).
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Nice essay, thanks for the link.
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EPT
