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I'm somewhat disturbed by the closure of this question: What is $9-5+2$?

It appears to be a mathematical question that is specific, answerable, and genuine - a "real" question. I can recall wondering the same thing when I first learned about addition and subtraction as a little kid.

The only "fault" is that it is extremely basic, but there are no rules against that, nor do I think there should be.

Thoughts?

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    $\begingroup$ It appears that sometimes closers choose random reasons for closure when there is no exact match for the real reason (the only possible choices are: exact duplicate, off topic, not constructive, not a real question, too localized). This has the unfortunate consequence that it may inadvertantly convey false messages to users about what is on-topic, or a "real" question, etc. See also my question here on related matters. $\endgroup$ – Bill Dubuque Apr 6 '12 at 21:44
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    $\begingroup$ Sometimes closing a question, after it has been answered, can be done to prevent additional useless answers. $\endgroup$ – GEdgar Apr 7 '12 at 13:05
  • $\begingroup$ @GEdgar: I've seen that many times across the SE network. $\endgroup$ – The Chaz 2.0 Apr 7 '12 at 16:17
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    $\begingroup$ @GEdgar One should never close a question to "prevent additional useless answers" because that also prevents additional useful answers. $\endgroup$ – Bill Dubuque Apr 7 '12 at 17:51
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    $\begingroup$ @GEdgar we can't prevent useless answers, by closing or downvoting questions but downvoting the answers themselves. $\endgroup$ – checkmath May 15 '12 at 12:02
  • $\begingroup$ I have sympathy for the mentioned question because it deals with the really stupid and misleading acronym BEDMAS, where the issue was that the questioner thought division had to come before multiplication and addition before subtraction (as the silly acronym misleads one to believe). $\endgroup$ – person27 Apr 6 '14 at 2:23
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Note: Closure does not automatically imply that the question is non-mathematical. I agree that there are interpretations of the question which make it on-topic and useful to folks, but that does not necessarily mean that we must keep it open.

The close reason is not quite right unfortunately, but I do agree with the closure, and that is not because it is basic (i.e. you seem to be deriving the wrong conclusion about the reason for closure), but because it is a dupe of one of the following, based on how you interpret it (thanks to Didier for the list).

What is the standard interpretation of order of operations for the basic arithmetic operations?

Do values attached to integers have implicit parentheses?

What is 48÷2(9+3)?

Also, the main question seems to be (ignoring the motivation): "Why my calculator does not follow a (supposed) rule". In one interpretation, that question (about the calculator) is not really mathematical, and is more about the interface on how to input numbers and figuring out the precedence which the calculator uses, and is out of the scope of this site. This was the reason I cast the last close vote (hastily, I admit. To be fair to myself :-P, I knew that in another interpretation, the question is a dupe).

Basic questions are welcome on this site.

Badly written, ambiguous dupes of existing questions, at whatever level, are not.

Also, closing a question does not mean it is gone forever. The OP can edit the question to make it clearer, and then the question can always be reopened (perhaps by making a meta post, like you did).

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    $\begingroup$ I do not think this question covers quite the same material as the duplicates suggested. These questions barely refer to subtraction, nor do they have a relevant example. The first question you suggested was created (following discussion on meta) as an attempt to cover cases like this - but it does not cover this case adequately IMHO. $\endgroup$ – Ronald Apr 6 '12 at 20:49
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    $\begingroup$ @Ronald: Can you please explicitly state what you think the question is really asking and why it is not a dupe/minor variant of one of those three I linked above? You are interpreting the question one way, which is possibly different from how I interpreted it (or some others did). That itself is a problem with the question (and what I referred to above by calling it ambiguous). Btw, the question and answers to the first question I linked are community wiki for a reason: Feel free to improve upon it! $\endgroup$ – Aryabhata Apr 6 '12 at 21:13
  • $\begingroup$ I believe the questioner's intent is to ask why the result on his calculator does not match his understanding of the standard order of operations. I don't believe that is unclear. He asks clearly "What is 9-5+2?" and "Why don't calculators follow [the given order of operations]?" This is far clearer a question than e.g. math.stackexchange.com/questions/124474/…, which has 3 upvotes. $\endgroup$ – Ronald Apr 6 '12 at 21:15
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    $\begingroup$ @Ronald: And why doesn't the highest voted answer to math.stackexchange.com/questions/33215/what-is-48293 answer this? $\endgroup$ – Aryabhata Apr 6 '12 at 21:18
  • $\begingroup$ Because it does not correct the questioner's misconception of BODMAS; nor does it give the canonical order of operations used by the questioner's calculator. $\endgroup$ – Ronald Apr 6 '12 at 21:20
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    $\begingroup$ @Ronald: So? The fact that there are different conventions is enough to answer the query that you could potentially get different results depending on how you input the numbers into the calculator (irrespective of whether you made a mistake when doing it manually). That is clearly answered by a combination of the three questions. btw, the fact that the questioner made a mistake in applying BODMAS is probably what prompted the "not a real question" close vote. If you want to address the manual error made by OP, then this becomes too localized, and really not of much help to others $\endgroup$ – Aryabhata Apr 6 '12 at 21:25
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    $\begingroup$ (Imagine multiple such questions...) $\endgroup$ – Aryabhata Apr 6 '12 at 21:30
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    $\begingroup$ It is partially answered by a combination of the three questions, and not well. The question of addition and subtraction priority is not directly addressed in any of the questions or answers I saw. None of the other questions address this particular, common misconception relating to the mnemonic "BODMAS". $\endgroup$ – Ronald Apr 6 '12 at 21:30
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    $\begingroup$ @Ronald: Then please edit the existing answers, or add a new answer to the existing questions and answer the previous question in its full generality (as they were supposed to have been). The question is a dupe, irrespective of whether the previous answers answer it satisfactorily (which IMO, is debatable here) or not. $\endgroup$ – Aryabhata Apr 6 '12 at 21:32
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    $\begingroup$ @Ronald: I am sorry. They do cover this (unless you think + and - are not basic arithmetic operations). If I ask another question: " What is 9-2+3-4*6", that is not a dupe, according to you? $\endgroup$ – Aryabhata Apr 6 '12 at 21:34
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    $\begingroup$ @Ronald: What about a/b-2/c+5%77^43? or 1/2/3/4/5-6/7+4? or ... ad infinitum. $\endgroup$ – Aryabhata Apr 6 '12 at 21:35
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    $\begingroup$ @Ronald: There is nothing novel (subtraction) as you claim. This is already covered with "basic arithmetic operation" in the first linked question (which even mentions it). And isn't BODMAS covered by one of BEDMAS, PEDMAS? The answer even mentions calculators! $\endgroup$ – Aryabhata Apr 6 '12 at 21:42
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    $\begingroup$ I think the problem is math at that level is innately repetitive and non-conceptual. Students at that level will do thirty homework problems that all test the same concept. That's why most basic questions tend to be duplicates to us math people (although the students probably think they're all different...) $\endgroup$ – badatmath Apr 6 '12 at 21:47
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    $\begingroup$ @Ronald: I suggest you read: meta.math.stackexchange.com/questions/1756/… and meta.math.stackexchange.com/questions/1868/… $\endgroup$ – Aryabhata Apr 6 '12 at 22:01
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    $\begingroup$ The question is certainly well answered by Wikipedia (the second result for me when googling "BODMAS"): "These mnemonics may be misleading when written this way, especially if the user is not aware that multiplication and division are of equal precedence, as are addition and subtraction. Using any of the above rules in the order "addition first, subtraction afterward" would also give the wrong answer." $\endgroup$ – Michael Greinecker♦ Apr 7 '12 at 11:58
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I agree this is a real question - in fact, I think it's a very important mathematical question.

The FAQ for Math.SE says: "We welcome questions about: Understanding mathematical concepts and theorems" and "Mathematics - Stack Exchange is for people studying mathematics at any level" (emphasis mine)

I believe this is a question directly about understanding a mathematical concept (a concept which is poorly understood amongst laypeople).

I think there is some fatigue in answering this question, especially as there has been a recent internet meme on order of operations which generated some tiresome arguments (even amongst mathematicians).

However, there is obvious value in answering this question clearly. I think it reflects badly on us, as a community, that we dismiss this question without giving it due consideration.

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    $\begingroup$ In one interpretation, it is actually not a real question! The user made a mistake, and then asks "Why doesn't the calculator follow BODMAS?". There is no answer for that :-) It is like asking, "when will you stop hurting puppies?". I believe that might have been the reason you see a "not a real question" vote... $\endgroup$ – Aryabhata Apr 6 '12 at 22:03
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    $\begingroup$ If users never made any mistakes, there would be no need for this site to exist. I suggest that many questions begin with a user's misconception and/or with the goal of resolving an apparent contradiction. The first question I looked at, i.e. math.stackexchange.com/questions/128837/… has a remarkably similar structure. $\endgroup$ – Ronald Apr 6 '12 at 22:17
  • $\begingroup$ I am just trying to guess the reason why we got a "Not a real question" close vote. I am in no way suggesting that that is a reason to close questions, as I clearly stated in my answer... $\endgroup$ – Aryabhata Apr 6 '12 at 22:19
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    $\begingroup$ I do not believe that the OP gave a good faith effort to ask a well-formed question. If he has seen anything on the subject of "order of operations", he will have seen examples of how things work. I voted to close because it showed no effort (which is reason to downvote) and because it was a duplicate of a mischievious question (the 48÷2... one). $\endgroup$ – The Chaz 2.0 Apr 7 '12 at 4:16
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    $\begingroup$ Lots of questions are based on misconceptions and a answer explaining why the question is illposed can be a worthwile experience. Here is a high-level example from MO. $\endgroup$ – Michael Greinecker♦ Apr 7 '12 at 12:04
  • $\begingroup$ I tend to agree with the view presented here by Ronald, though it appears many people do not so I don't think it would be fair to "accept" this answer. $\endgroup$ – Nick Alger Apr 8 '12 at 6:12
  • $\begingroup$ You don't have to accept any answers if you don't want to! $\endgroup$ – The Chaz 2.0 Apr 8 '12 at 17:42
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I interpret the total lack of response by the OP to commentors/answerers as a sign of bad faith.

As for the points in Nick's meta question, if this were a specific question - namely the one in the subject - then the answer would be "SIX". Nine minus five plus two is six.

If the question is "why don't calculators follow that rule?", then the answer* is "they do, mostly".

But what is the motivation for this question? A guy "learns" about BODMAS - enough to be giving us reminders! - and then ... well I don't know. It could have been a simple mistake, but then again, he could have just said so. He didn't. Bad faith.

The fault is not in it being a basic question. Many borderline questions (this comes to mind) have been asked and answered.

*Back when the 48÷2(9+3) thing hit the internets, I was active on 4 forums that were spammed with that garbage. One interesting revelation (I think from physicsforums.com/org/something) was that different math software interpreted the ambiguity of 48/2(12) differently.

/drunken rant

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  • $\begingroup$ "total lack of response by the OP": for the record, the OP accepted an answer, almost as soon as it was posted. $\endgroup$ – Ronald Apr 7 '12 at 10:06
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    $\begingroup$ I saw that, @Ronald, as well as his edit three hours after the original. Accepting an answer requires one mouse click, and can hardly be called a response. It's already on the record... $\endgroup$ – The Chaz 2.0 Apr 7 '12 at 13:26
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It would have been much better if someone had written a comprehensive answer and further similar question would be closed as duplicates.

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  • $\begingroup$ A comprehensive answer would have to delve into the issue what x+y-z means when "+" and "-" stand for any binary operations (though not necessarily with the term "binary operation" of course). Such an answer, I think, will end up implying that either you need to have a preferred convention for these sorts of expressions, or that such expressions except in special cases where conventions are clear, are ambiguous. If the former, then the answer to the question relies upon an arbitrary choice made for operation evaluation. If the latter, then the question has no answer. $\endgroup$ – Doug Spoonwood Apr 9 '12 at 12:40
  • $\begingroup$ I disagree that a comprehensive answer to someone posing this question has to include any binary operation. $\endgroup$ – Phira Apr 9 '12 at 20:42
  • $\begingroup$ If you take +, and - have variable arity in a context where we only have equations like x-y+z, how do you explain that "+" always behaves like a binary operation? $\endgroup$ – Doug Spoonwood Apr 9 '12 at 23:23

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