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chonkyfire
United States451 Posts
On April 09 2011 04:32 VisuaL. wrote: I'm currently in school to be a chemist and i took a math course in fall. I got 288 and 1/(2*x) was pretty easy and don't see how it can be 2 :s If it's 1/(2*x) how can it be anything but 2? | ||
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Bhaalgorn
Slovenia214 Posts
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Shadowcloak
Netherlands194 Posts
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FrozenFrog
Singapore133 Posts
On April 09 2011 04:35 Bhaalgorn wrote: Good job at tricking people into voting for 2, you sure as hell got me. Bet the OP would make for a very hated math teacher. Yea got me too xD | ||
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DemiAlbedo
Canada69 Posts
B - Bracketes E - Exponents D - Divide M - Multiple A - Add S - Subtract. 48 ÷ 2(9+3) = 48 ÷ 2(12) = 24(12) = 288 | ||
MasterOfChaos
Germany2896 Posts
On April 09 2011 04:37 Shadowcloak wrote: why does it ask math at university lvl this is high school material Because the notations an conventions used can vary between school and university. And this is a question about what convention you assume for omitted multiplication. | ||
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ChrisXIV
Austria3553 Posts
On April 09 2011 04:32 VisuaL. wrote: I'm currently in school to be a chemist and i took a math course in fall. I got 288 and 1/(2*x) was pretty easy and don't see how it can be 2 :s By reading the first one like you did the second. Because if you want to be consistent it has to be 1) 2 and 1/(2x) or 2) 288 and x/2 otherwise you are contradicting yourself. | ||
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Ceril
Sweden1343 Posts
On April 09 2011 04:42 ChrisXIV wrote: By reading the first one like you did the second. Because if you want to be consistent it has to be 1) 2 and 1/(2x) or 2) 288 and x/2 otherwise you are contradicting yourself. 1/2x is not all numbers, its variables. and hence 2x got a silent bracket around it to denote the 2 and x belong togheter. 1/(2x) | ||
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TBO
Germany1350 Posts
http://mathforum.org/library/drmath/view/57021.html but there it is said that the AMS convention is that "multiplication indicated by juxtaposition is carried out before division." | ||
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Sluggy
United States128 Posts
On April 09 2011 04:37 Shadowcloak wrote: why does it ask math at university lvl this is high school material order of operations is elementary school material. The interest of the poll is how people studying math at a high level can overlook the standard way of evaluating expressions. It doesn't say anything about the ability of these people to understand elementary school concepts, but it does serve as a reminder that there are ambiguities in the way things can be evaluated and that is why standardized conventions exist in the first place. | ||
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Ace
United States16096 Posts
On April 09 2011 04:31 mpupu wrote: Don't take it personally. I'm not trolling anyone and I never said you were "less qualified" or anything like that. But if the only guideline you know is PEMDAS, you're missing the big picture. And saying you can't apply the distributive property is certainly wrong, that's 100% fact. I'll give you an analogy: let's say you know how the common SOH-CAH-TOA applies to trigonometric functions. Would you dispute it if I told you that sine is a trascendental function defined in terms of infinite series? After all, it's just a relation between the lengths of different sides of a triangle, right? What does that have to do with *anything* here? If you have another method then show us but there is no "big picture" here. It's very simple, basic math. Here let's do it like this: 48 ÷ 2(9+3) Let's rewrite it so there is no division. Remembering that multiplication is the reciprocal of division: 48 ÷ 2(9+3) = 48 * 1/2*(9+3) Notice I'm using the original post by the OP so there is no confusion with the "/" sign. There isn't any advanced version of this stuff any further than this. No matter what you try to do the answer will be 288. You can distribute the 1/2 to the parenthesis and end up with 48 x 6 , use PEMDAS and up with with 24 x 12, multiply them in any order - it will always be 288. On April 09 2011 04:40 DemiAlbedo wrote: I answered 288, but after reviewing some of the comments a lot of people were discussing how they obtained the answer using "PEMDAS". I Feel stupid because I have never heard of PEMDAS. In Elementary School we were taught BEDMAS <-- Canadian education system maybe. B - Bracketes E - Exponents D - Divide M - Multiple A - Add S - Subtract. 48 ÷ 2(9+3) = 48 ÷ 2(12) = 24(12) = 288 They are the same thing. People are just using them wrong by assuming Brackets/Parenthesis means implicit multiplication without taking into account there is a term on the left of it. | ||
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Roggay
Switzerland6320 Posts
On April 09 2011 04:42 ChrisXIV wrote: By reading the first one like you did the second. Because if you want to be consistent it has to be 1) 2 and 1/(2x) or 2) 288 and x/2 otherwise you are contradicting yourself. The "2" in "2x" can be interpreted as the coefficient of x, however there is no x in 48÷2(9+3). | ||
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shadowy
Bulgaria305 Posts
On April 09 2011 04:47 Ceril wrote: 1/2x is not all numbers, its variables. and hence 2x got a silent bracket around it to denote the 2 and x belong togheter. 1/(2x) Variables or constants - it's all the same. Both cases there is silent bracket...or at least thats point some people are trying to get across. Which leads us again to poorly written and contradicting equation in first place. | ||
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Roggay
Switzerland6320 Posts
On April 09 2011 04:48 Sluggy wrote: order of operations is elementary school material. The interest of the poll is how people studying math at a high level can overlook the standard way of evaluating expressions. It doesn't say anything about the ability of these people to understand elementary school concepts, but it does serve as a reminder that there are ambiguities in the way things can be evaluated and that is why standardized conventions exist in the first place. The standard convention requires parenthesis for such cases, atleast its what they taught me at school here, and its more logic this way. | ||
micronesia
United States24761 Posts
On April 09 2011 04:23 chonkyfire wrote: No now you're not doing the brackets first. If you distribute you do that brackets first. If you did the brackets first you get 48/24 Distributing is not a bracket/parentheses operation... it is multiplication. Thus, you can only distribute if you are allowed to multiply the 2 by the the expression in the brackets. You can not multiply the 2 by the (9+3) yet. Multiplication and Division have equal weight and occur from left to right in a one-liner mathematical expression. The division must be done before the multiplication according to strict math rules. Thus, it is not acceptable to distribute the 2 into the 9+3 before doing 48/2. | ||
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mpupu
Argentina183 Posts
On April 09 2011 04:50 Ace wrote: What does that have to do with *anything* here? If you have another method then show us but there is no "big picture" here. It's very simple, basic math. Here let's do it like this: 48 ÷ 2(9+3) Let's rewrite it so there is no division. Remembering that multiplication is the reciprocal of division: 48 ÷ 2(9+3) = 48 * 1/2*(9+3) Notice I'm using the original post by the OP so there is no confusion with the "/" sign. There isn't any advanced version of this stuff any further than this. No matter what you try to do the answer will be 288. You can distribute the 1/2 to the parenthesis and up with 48 x 6 , use PEMDAS and up with with 24 x 12, multiply them in any order - it will always be 288. The "other method" has been mentioned several times in this thread: assigning higher precedence to implicit multiplication. But you seem to think PEMDAS is the only valid approach. If you don't want to change your mind, that's your prerogative. Otherwise, the link provided above is a good reference for what I'm trying to say (http://mathforum.org/library/drmath/view/57021.html). | ||
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mpupu
Argentina183 Posts
On April 09 2011 04:54 micronesia wrote: Distributing is not a bracket/parentheses operation... it is multiplication. Thus, you can only distribute if you are allowed to multiply the 2 by the the expression in the brackets. You can not multiply the 2 by the (9+3) yet. Multiplication and Division have equal weight and occur from left to right in a one-liner mathematical expression. The division must be done before the multiplication according to strict math rules. Thus, it is not acceptable to distribute the 2 into the 9+3 before doing 48/2. The point is that it's possible to distinguish between implicit and explicit multiplication, and assign different weight to both. In that case, implicit multiplication occurs first and the distributive law can be correctly applied. | ||
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Pufftrees
2449 Posts
On April 09 2011 03:58 levelnoobz wrote: BTW I really don't see the point of those 81 pages appart from proving that if you write maths like this nobody will understand you. By 'nobody' you mean anyone who doesn't understand how math works I imagine. | ||
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ChrisXIV
Austria3553 Posts
On April 09 2011 04:47 Ceril wrote: 1/2x is not all numbers, its variables. and hence 2x got a silent bracket around it to denote the 2 and x belong togheter. 1/(2x) Variables are stand-ins for numbers if I'm not mistaken. Is there a rule for the "silent bracket"? | ||
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Sluggy
United States128 Posts
On April 09 2011 04:52 Roggay wrote: The standard convention requires parenthesis for such cases, atleast its what they taught me at school here, and its more logic this way. Here standard convention means the accepted way of handling things. The standard at your school could be to parenthesize everything so that no ambiguities can exist, but in general you don't need parentheses to evaluate it if you follow a convention. The standard convention says division and multiplication have the same precedence so how do you choose? The standard is to then evaluate expressions from left to right if the precedence is the same. Ambiguity is eliminated after that. I could state my own convention that once precedence is established to evaluate from right to left, but it wouldn't be standard. You could also do establish 'implicit vs explicit multiplication' and give implicit a higher precedence than explicit, but that isn't widely used and therefore not standard in the sense I'm talking about. The point still stands, it isn't about people's ability to do basic arithmetic - just boring semantics. | ||
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