Presenting an expository paper that has already been accepted by a magazine I am an undergraduate student in mathematics and recently I have written an expository elementary paper that got accepted by a magazine (I wouldn't call it a journal, because it mainly focuses on olympiad-type questions, not on reseach) aimed at high school students (in case it is relevant, my paper presents some advanced tools that may come in handy when dealing with olympiad problems and then goes on to actually show some applications to such problems).
Now, my university organises a conference for undergrads where we are encouraged to present papers that contain interesting ideas (they specify that the results needn't be original and they also needn't be research level, they just want to encourage undergrads to do some kind of research). I would like to make sure that, given these conditions, it is ethical to submit my paper to this conference. Of course, I will definitely mention that my work is going to be published in that magazine. I don't see any problem with this, but I am young and unexperienced, this is why I want to make sure that I am not doing something bad. I am not even sure that my question is fit for this forum, because I am talking about an expository paper, not a research paper, but this place seems to be the best place to ask my question.
EDIT: I forgot to state this, but I will definitely let the editors of that magazine know about me wanting to present the paper to that conference, I just want to make sure that from an academic viewpoint this looks all right.
Since you will inform everyone about the situation, there are no further ethical concerns. You need to cite the earlier work in the later one as usual, of course. And the submission to the conference may be accepted there or not, depending on the judgements of others. You are making it possible for that to be an informed judgement, so all is well.
The citation avoids any possible charge of self plagiarism.
I would also give the same answer if it were a research journal and a professional conference. If you give the impression (vocal and written) at the conference that you are presenting prior work, rather than new, it would be fine. Expository talks on existing research should raise no issues. There are ways to step over the lines of propriety, but this isn't one of them.