I got 83% in 10th 77% in 12th n 76% in graduation (bba) does i get iim if my percntile is above 90?

You have a pretty decent academic records but 90 percentile are not enough for anyone to get a call from any IIM. Even if you are a non engineer who basocially gets a call at lower percentile than an engineer student of same category still with 90 percentile getting a call from IIMs is very low.

You need to understand the procedure after CAT exam every IIM makes a merit list to call students for next round of interview and WSAT, based on your aggregate score which comprises of many factors such as CAT marks, 10th 12th and graduation percentage, work experience, engineer or non engineer, gender with different weightages for different IIMs. In this in most of the IIMs CAT marks have the highest weightage around 35-60%.

So to get calls from top 3 IIMs i.e. IIM A, B and C you need to score above 99+ percentile. For other old IIMs like IIM L, K and I you need to score above 97+ percentile to get a call for next round. And by scoring above 93+ percentile you will have a good probability of getting a call from new IIMs. The above figures are rough figures based on previous years data and I have already told you along with your CAT marks your profile also matters a lot. So always aim for high percentile in order to increase probability of getting a call and converting your call.

All the best for your preparations and exams!!