I've been skimming through some unanswered questions, and have come across some where the OP has left a comment saying "I figured it out--never mind," and no answers have been posted.
On questions like these that are somewhat common (e.g. finding the volume of a solid of revolution from Calc II homework), should we vote to close? Also, what reason would we select to close the question?
I am in favor of closing these types of questions as it helps reduce the "Unanswered Questions" count, and the marginal benefit of an additional example of finding the area under $x^2$ on the range $[1, 2]$ (or a similar problem) is small.
Another option for questions like these that have a $0$ net score is to vote them down to $-1$, and let them be auto-deleted after so many days.
So, my question really is:
What should we do with common sorts of questions that the OP is no longer interested in receiving an answer?
Do we vote to close (and under what reason), or do we vote down (and allow an auto-delete), or do we do nothing/answer the question?