Yes! And you should revisit questions that you answered correctly. :)
It doesn't matter that you know the answer. The goal is not to memorize the answer - you won't see this question on the test, right?
In fact, of all of the questions that you study, you won't see a single one on the test. What you're trying to learn is not that exact question but
how to think your way through the kinds of questions that they write. And as you get better, you can actually go back and learn things that you weren't yet good enough to understand or notice before.
So you may look at the question and think, yep, the answer is B and I did it via method XYZ last time. This time, think: hmm. Is there another way to do it? Maybe there's a faster or easier way. What about traps - what kind of traps are they setting for people? The better you get at spotting traps, the less likely you will be to fall for similar ones on the real test.
It's often easier to spot traps or figure out more efficient solutions methods on questions that you got right, by the way - or on questions that you've seen before, so you're more familiar with them.
This is why you want to study in this way:
http://tinyurl.com/executivereasoningThis is how to study this way:
http://tinyurl.com/2ndlevelofgmatTry that out and let me know what you think!