I think an easier way to think about admission is through your GMAT score, rather than thinking about what score you'd have to get to achieve the type of school on a ranking system. Focus on your GMAT first and aim for 800. Then with a score in hand, it'll be easier to say which range may suit you better. Otherwise, it's all generic one way or another - top 20 b-school, aim for 700+, top 30, aim for 650+, top 40, aim for 600+.
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