# Why do obvious duplicate questions on MSE get upvoted, answered, and their answers upvoted?

The title is the question: why do obvious duplicate questions on MSE get upvoted, answered, and their answers upvoted? And what can be done to prevent this? Here is an example: https://math.stackexchange.com/questions/576520/does-sum-n-1-infty-frac-1-n-diverge . This question had about 3 upvotes when I saw it, and several people answered it. One of the answers had 5 upvotes! Probably many of the people who answered knew that the question was almost certainly a duplicate. I don't blame the OP, who probably had no idea. I saw the same thing happen a week or two ago when, for the umpteenth time, someone asked how to evaluate $\int_0^\infty e^{-x^2}\,dx$.

I don't think the same question should get answered multiple times on MSE unless someone has a truly original answer, and there are only so many good ways to show the harmonic series diverges. I know I can flag such questions as duplicates, and leave a comment to the OP with a link to a previous question. I can downvote an answer because it is certainly equivalent to a previous answer to the same question. But I think downvoting answers costs me a small number of points, so I'm reluctant to do it.

By the way, there is a related question at: http://meta.math.stackexchange.com/questions/4975/downvoting-because-of-duplication

I had trouble thinking of good tags for this question, so feel welcome to add more or remove the ones I used if you don't think they fit. There is an (exact-duplicate) tag, but I'm guessing it is for people who go fishing for answers to their homework problems by asking the same question several times.

• To clarify: downvoting an answer costs you 1 point. Downvoting a question is free. – Nate Eldredge Nov 22 '13 at 1:29
• @NateEldredge : Thanks. I should now this by now, and it is probably in an FAQ somewhere, but is duplication considered a valid reason for downvoting a question? If I downvote a duplicate question, does it cost the (usually innocent) poser of the question any reputation points? – Stefan Smith Nov 22 '13 at 2:02
• See this thread from last summer. – Jyrki Lahtonen Nov 22 '13 at 7:58
• @Jyrki: Now everybody knows what you did last summer. – Asaf Karagila Nov 22 '13 at 11:07
• A good answer is a good answer, irrespective of whether the question is a duplicate. – Brian M. Scott Nov 22 '13 at 19:31
• @Brian, it's better to have all the good answers to any given question in one place, not scattered around. If you have a good answer to a duplicate problem, close the duplicate and post the new answer at the original. – Gerry Myerson Nov 23 '13 at 6:04
• @Gerry: I don’t feel strongly either way, but I don’t disagree. However, that wasn’t my point. My point is that voting on an answer should be determined solely by the answer and its relationship to the question. There is nothing wrong (and much right) with upvoting a good answer to a duplicate. – Brian M. Scott Nov 23 '13 at 15:49
• @Brian, OK, I misunderstood your comment. – Gerry Myerson Nov 24 '13 at 4:06