In Stack Overflow new questions are focused on a lot even after the OP gets the required answer and marks his question as answered. Still the question remains at the top of the questions list. The new questions posted and left unanswered are moving off the list and nobody is looking at those questions. So, what I suggest is that answered questions will immediately move out of the questions list. This will reduce confusion, time and helps users to focus on other questions. So rather than answering an answered question, I feel the questions that are left unanswered for more than a day should get some kind of priority to get answered.
From my personal experience I posted a question for which I didn't receive any answer, and later I posted the same question with some modifications for which I was answered within minutes. It just depends on the level of experts that are present at the time of posting questions, but when my simple previous question was not answered, I posted the same question later and got the perfect answer. So, please consider this and remove the answered questions from list of recent questions so that unanswered questions will have more chances to get answered.