what is a good score which yields you 98+ percentile in CAT exam ? How many questions should be attempted and how many of them should be correct?

Hi Shiksha,
What score can yield you a 98+ percentile is a very subjective question. The main reason being is that CAT is an exam where your relative performance matters. If the paper is tough you might get 98 at 130-140 whereas in an easy paper 165 might also not be enough. Another reason which makes it difficult to predict is because CAT authorities do not reveal your raw score. What you get in your scorecard is your scaled score.
Still if you want an answer, for last two years a scaled of around 165-170 lead to a 98 percentile whereas the scaled score for 99 percentile was 192 in 2014 and 180 in 2015. An attempt of around 75 question with 80 percent accuracy can fetch you that score.