I recently answered a question I later found to have been asked nearly 3 years ago. If interested the question is Constructing a family of sets. (EDIT: The answer I provided was not correct, but this question remains interesting to me)

My question is if it is frowned upon to do so. I know on one hand that the website benefits with less answerless questions, but on the other hand it is much like speaking to the void---no one is going to listen/contribute/notice (beyond the admins), so why bother?

I guess ultimately my question is about answering questions with "activity." I just want the community's thoughts about the distinction of being useful to admins vs being useful to the Math SE community.

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    $\begingroup$ You should consider also whether your answer is really adding something. This is a reasonable thing to consider even for new questions which may not yet have been answered, but I believe it is certainly much more annoying when the question is "old" and the answer is poor. There are people here that "answer" years-old questions with answers that are either wrong, incomplete, or just off-topic. Don't do that. $\endgroup$ Commented Feb 16, 2019 at 14:00
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    $\begingroup$ Perhaps it might change your perspective if the primary goal of Stack Exchange is to build a repository of high-quality Q&A, with helping the asker as a secondary goal. $\endgroup$
    – Andrew T.
    Commented Feb 17, 2019 at 5:00
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    $\begingroup$ @AndrewT. I'm not quite sure if you are posing a hypothetical situation or if you are actually stating you believe the primary goal is building a high-quality Q&A repository. In the latter case, my understanding, hope & belief is that it's the other way around, i.e., the primary purpose is to help the questioner, with building a repository being a secondary consideration. However, as Trevor Gunn's answer explains, if the asker is not around any more, or likely not interested, then answering any such questions would then only have a primary purpose of adding to our repository of quality Q&A. $\endgroup$ Commented Feb 17, 2019 at 19:11
  • $\begingroup$ @JohnOmielan Related older discussion: What is the purpose of this site? $\endgroup$ Commented Feb 28, 2019 at 14:21
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    $\begingroup$ @MartinSleziak Thanks for the link. I've read it, plus several other related linked questions. The various points made were interesting & very elucidating. I should've known & expected a site as relatively large & varied as this one, plus which doesn't have a strong top-down hierarchy, would have a diverse set of views, goals & experiences. Your linked question, & the other ones I read, are all from over $5$ years ago, so they might not be completely applicable now, but I don't think it's changed very much. Although each of us are different in some ways in how we view & use this site, cont. $\endgroup$ Commented Feb 28, 2019 at 22:41
  • $\begingroup$ @MartinSleziak I believe our similarities in this regard is more than our differences. We can have different goals & approaches but still work well together to keep this site running well. Despite some issues I have with a few things, overall I believe this is a great site which I'm glad to be a small part of. As an experienced computer programmer (over $30$ years), I have a fairly good idea of the large amount of time & effort put into the programming for running this site. Although it can be improved (which is true for almost all software), it has many excellent features & is very powerful. $\endgroup$ Commented Feb 28, 2019 at 22:45

2 Answers 2


From a purely practical point of view: how you answer an older question might be different than how you answer a new question.

Is frowned upon to do so?

There's nothing frowned upon. The only answers people frown upon here are when people post complete solutions to homework problems where there is no apparent effort in the question to solve the problem.

For your example, the person asking the question last visited the site in March 2016 (almost 3 years ago). Meaning when you answer their question, most likely they won't see your answer. Therefore you probably want to write your answer with the community in mind rather than the person asking the question. This stuff you put into your answer:

Have you considered the following?

Let me know if you need more details.

It's strange because there's a good possibility the person asking the question is never going to see your answer.

I suggest the following practical advice:

  • If the person who asked the question is still active on this site (which you can see from their user profile) then you can treat the old question the same as any other question.

    • Although if it looked like a homework problem when it was posted, it's probably not the questioner's homework anymore.
  • If the person who asked the question hasn't been seen in months or years then generally your answers should be useful to the community and the person who originally asked the question is all but irrelevant.

    • If an answer seems like it would only be useful to the person who asked the problem, then your time is better spent on other questions.
    • If you're giving hints rather than a complete solution, then tailor your hints to the problem rather than the work shown in the question (because if it's tailored to the work shown then it's tailored to the questioner).
    • Possibly this involves repeating some of the work shown in the question as part of the solution sketch.
    • If I lean a certain amount towards giving hints rather than complete solutions to new questions, I might lean a little more towards complete solutions for older problems. For new questions, if your hint or lack of details confuses a large number of people, then you will get a follow-up comment right then and there. If it's an old question, it might be months before someone comes across your answer with follow-up questions.
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    $\begingroup$ This answer changed my perspective that it is indeed still valuable to answer some old questions with the caveat that the answer should target the wider audience instead of the OP. $\endgroup$ Commented Feb 16, 2019 at 9:27
  • $\begingroup$ I basically completely agree, but I would add an extra qualification re: treat the old question as any other if the asker is still active, apart from homework type problems. There are other question types which are more transactional, i.e., the asker may have been interested in it then, but not now. Of course, that's often hard to tell, but then even determining "homework" type problems is not always cut & dried. Regardless, if in your judgement you believe the person is likely not particularly interested in the answer now, then I suggest to try to answer it for the general audience instead. $\endgroup$ Commented Feb 17, 2019 at 19:24

I think that some people are just making the assumption that for almost all old questions, if there was another potential answer that added something to the already existing answers, one would have been added earlier already. I think some of those people are actually overconfident about that being the case for some of the questions that it's not the case for. I wrote an answer to Well-orderings of $\mathbb R$ without Choice. At first, AsafKaragila wrote a comment that I believe was saying how I shouldn't write an answer of my own 2 years after Noah Schweber's excellent answer. Later, I saw that that answer of mine had an upvote and that comment no longer existed.

I've also seen a lot of Mathematics Stack Exchange questions where none of the answers were accepted. I left like I figured out what the question asker's confusion may have been and saw that the other answers were nothing like how I would have written one so I wrote my own. One such question was What is special about glide reflection?. I cannot know what other users are thinking. I can only know what I'm thinking so I had to refer to a question I answered myself.


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