EPTOn April 08 2011 07:44 de1irium wrote:
http://xkcd.com/169/
http://xkcd.com/169/
O holy night, the stars are brightly shiiiiiiininggggg...
A Simple Math Problem? - Page 25
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StallingHard
144 Posts
O holy night, the stars are brightly shiiiiiiininggggg... | ||
micronesia
United States24780 Posts
On April 08 2011 07:51 jcarlson08 wrote: I think the context of the OP made it quite clear that the formulae were to be assumed correct as written. Before the mod edit the context of the OP was actually somewhat different, just so you know. This used to be a thread about a math discussion on a bodybuilder thread :p | ||
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Mailing
United States3087 Posts
![[image loading]](http://imgur.com/HvN5t.jpg) | ||
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Usyless
54 Posts
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Chimpalimp
United States1135 Posts
PEMDAS The order of precedence occurs as such: 1. Parenthesis 2. Exponent 3. Multiplication = Division 4. Addition = Subtraction When given the case that there are two operations which have equal precedence, always do the first one. This is the reason the correct answer is 288 and not 2. The same holds true for problem 2: the answer is (1/2)*x not 1/(2*x), because the division comes before the multiplication. Not to insult anyone but if they write 1/2x to mean 1/(2*x), they are just being lazy with their notation. Any of my professors would count my answer wrong if I wrote 1/2x to mean 1/(2*x). | ||
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micronesia
United States24780 Posts
On April 08 2011 07:51 billyX333 wrote: i'm getting quite tired of people analogizing the ambiguity of 1/2x with 48/2(9+3) because it isnt the same. with 1/2x, the only question is if w. its obviously going to be interpreted as 1/(2x) because no body is going to attempt to convey x/2 as (1/2)x without using brackets The same argument works the other way though, nobody would reasonably express the question in the OP as 48/2(9+3)... well actually some would because they are morons and I hate when people do that so much. | ||
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munchmunch
Canada789 Posts
On April 08 2011 07:51 billyX333 wrote: i'm getting quite tired of people analogizing the ambiguity of 1/2x with 48/2(9+3) because it isnt the same. with 1/2x, the only question is if w. its obviously going to be interpreted as 1/(2x) because no body is going to attempt to convey x/2 as (1/2)x without using brackets Maybe this is not what you were getting at, but the concept was originally introduced to point out that there are actually two usages: "expressions to compute", and inline fractions. | ||
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MandoRelease
France374 Posts
On April 08 2011 07:10 mikeymoo wrote: It really depends on the context. You would never see a formula typed out linearly like this in any paper. It's like reading "cos2x" and arguing that technically it should be equal to cos(2)*x when most people would see cos(2x). I made an assumption about the equation because it's being asked in the first place. Most arithmetically sound people wouldn't ask this question on a forum, so I assumed that the author was bad at math. Someone bad at math would definitely phrase this question as something he/she had seen on his/her homework, that is, they would write 48/(2(9+3)) as seen on homework as what was typed in the poll. Yes, it's technically 288. Usually if it is meant to evaluate to 288, it would be written (48/2)(9+3), for clarity. I'm not embarrassed at all to have answered 2. I strongly disagree with the bolded part. Math does not depend on the context. The poll asked for the answer of the calcul (computation ? I don't know what word to use sorry), and the calcul was crystal clear since omitting the mutltiplicative sign here is perfectly correct. However omitting the parentheses in "cos2x" is not, and has never been written as such in any accurate paper/article/book i've read. I don't believe your comparison is correct. As for thinking that the author was bad at math, I think it is a pretty weird assumption. As far as I'm concerned i've never seen 1/2x being interpreted as 1/(2x). But for the sake of the argument, i'll agree that it's pretty easy to be confused. However if one thinks that there's an ambiguity, one should make the author clarify his thoughts. Especially for something like mathematics, everyone has to work with the same standards in order to do anything, even something as basic as that. I really hate to see comments like "technically the answer is xxx but ...". It's like there are several ways to look at an equation while there is only one. Unless there's an obvious mistake in an equation, I like to assume that the author is rigourous enough to ask a question using mathematical standards and not cheap papers notations. That's why I don't like you assuming that the author is bad at math. | ||
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garbanzo
United States4046 Posts
On April 08 2011 07:53 Chimpalimp wrote: The reason most people got the first one wrong is that they assume that multiplication has precedence over divison, which is incorrect. PEMDAS The order of precedence occurs as such: 1. Parenthesis 2. Exponent 3. Multiplication = Division 4. Addition = Subtraction When given the case that there are two operations which have equal precedence, always do the first one. This is the reason the correct answer is 288 and not 2. The same holds true for problem 2: the answer is (1/2)*x not 1/(2*x), because the division comes before the multiplication. Not to insult anyone but if they write 1/2x to mean 1/(2*x), they are just being lazy with their notation. Any of my professors would count my answer wrong if I wrote 1/2x to mean 1/(2*x). That is not true at all! Read the thread please. | ||
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Aruno
New Zealand748 Posts
To me 48÷2(9+3) would be 48÷2x12 why? Because I always thought it was like this Parentheses first, multiplication second, division third, then minus/positive after that. But really the test in my eyes is what does Y÷Z(NUM) operation =? I frankly think the whole Z( <- point of assuming multiplication was always annoying. I felt Z should have the specification of Zx( always. To avoid assumption. Why couldn't I have been taught this shit in school. >_< Hate how shitty my teachers were. | ||
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micronesia
United States24780 Posts
On April 08 2011 07:53 Chimpalimp wrote: The reason most people got the first one wrong is that they assume that multiplication has precedence over divison, which is incorrect. As we have been discussing there is another major reason why people are 'getting it wrong.' It's not just because they didn't know that M and D are weighted evenly in PEMDAS. | ||
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rackdude
United States882 Posts
On April 08 2011 07:36 Zeke50100 wrote: I always learned that the P in PEMDAS means inside the parentheses, and nothing beyond that (and a quick google search confirms). I'm glad I'm learning math the right way ^_^ EDIT: Oh, and PEMDAS should really be written P/E/MD/AS, to avoid confusion. By the way, 1/2x has absolutely no ambiguity. It's definitely x/2; the 1/(2x) is a misconception, and 1/2x should actually never be written as a substitute for it. It's acceptable to write 1/(2x) with 1 above BOTH the 2 AND the X below the line, but not 1/2x. It literally means "1 divided by 2 times x". The words "the quantity" are so underused in life XD Or it could mean "1 divided by 2x". This is why they invented tex. I think the dumb part is that we are arguing about something that's written in a way that would be acceptable anywhere. If you try to turn that in, first of all you'll get an F for not putting it in LaTeX and trying to use Word like you were in elementary school, and second of all your teach would circle it's meaningless until you put more parenthesis around things. For it to be written correctly it either needs to be (48÷2)(9+3) or 48÷(2(9+3)) because the operations are only defined between two numbers. It's like how 2(9+3) is not really a number, but equals the number that would be (2(9+3)) People are trying to sound like they know lots of math because they know order of operations and calling everyone else stupid... come on, you sound like you're compensating for something. Lets talk complex analysis if you think you're so baller at math. | ||
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Zeke50100
United States2220 Posts
On April 08 2011 07:52 Mailing wrote: Holy shit, even the internet doesn't know o_o EDIT: Just kidding, I totally misinterpreted what you wrote. Sorry! You cannot change the formatting of the problem to what the image says, because that essentially sticks parentheses around areas that SHOULDN'T. The real problem is that people confuse single-line math with handwritten math, and how one translates exactly in to another. In single-line math, fractions with more than a single term in either the numerator or denominator exist only when parenthesis "block" them off. | ||
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FrozenPanDA
Canada17 Posts
On April 08 2011 07:48 Blisse wrote: Are you kidding? Look at the numbers that have voted in both polls. And look at how the divisor sign is written in both cases. I'm tired of these people pretending they're amazing and see everything perfectly. Because it's obvious they don't. No sir, I am not kidding. To get 288, the MAJORITY vote, you have to do (48/2)(12) which is the same as (1/2)*x, the MINORITY vote. To get 2, which was the MINORITY vote, you have to do (48)/(2*12) which is the same as 1/(2*x) if let 48=1 and (9+3)=x, and is also the MAJORITY vote | ||
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kaiz0ku
Greece289 Posts
48IIIIIIIIIIIII1 -----III*IIIII-------- 1IIIIIIIIIIII2(9+3) | ||
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Dtd
Sweden19 Posts
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Mailing
United States3087 Posts
On April 08 2011 07:55 Zeke50100 wrote: When written in a single line, it's interpreted just the way it's supposed to be, which is 288. You cannot change the formatting of the problem to what the image says, because that essentially sticks parentheses around areas that SHOULDN'T. The real problem is that people confuse single-line math with handwritten math, and how one translates exactly in to another. In single-line math, fractions with more than a single term in either the numerator or denominator exist only when parenthesis "block" them off. I did not change it, the computer changed 48÷2(9+3) to the first format itself... | ||
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jackarage
Canada104 Posts
48*(1/2)*(9+3)=288 and no mater which order you put is equal to 288 and when 1/2x is not writen as (1/2)x it is 1/(2*x) | ||
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Veritask
260 Posts
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munchmunch
Canada789 Posts
On April 08 2011 07:53 Chimpalimp wrote: Not to insult anyone but if they write 1/2x to mean 1/(2*x), they are just being lazy with their notation. Any of my professors would count my answer wrong if I wrote 1/2x to mean 1/(2*x). I wouldn't, unless there was actually a common way of getting the problem wrong that evaluated to (1/2) * x. Of course, some professors just like to be dicks to students. | ||
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