<p>Just to reopen this, it seems the current practice is often (2) <em>provide helpful hints</em>, particularly in comments to the question.  My view is that after a suitable period of time it is worth giving a fuller answer, as I did with <a href="https://stats.stackexchange.com/questions/8033/normal-distribution-homework">How to find percentiles of a Normal distribution?</a> 10 days after the question was asked. Is that reasonable?  </p>
