There was recently a question about calculation short-cuts to save time. I'd like to know what the community consensus is about the acceptability of such questions here.
I myself voted to close -- I'd say this has more to do with mental tricks than mathematics. I don't expect questions here to be MO-level, of course (in fact, I expect them not to be), but I think we should restrict ourselves to questions that are about doing and using mathematics.
Incidentally, I don't mind questions such as this one in moderation. This isn't a site about math education, but I don't see a problem with a few such questions, especially since it seems more serious (with a definite and productive purpose) than the previous one.