Hello,
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Mostly, your graduation marks will be considered rather then inter marks.
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So, the percentage you need in graduation is 50% and there 5% relaxation for SC/ST/PWD i.e,you should score 45%
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And coming to inter percentage you need to pass your intermediate with Atleast 50 to 60%.
So that you will not be facing any problems Futher.
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Coming to IIMs each IIM has there own Eligiblity criteria and there own cut-offs.
Some of the IIMs need 90% in there entrance examination where as some of them need 80%.
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Some of the IIMs co-operate with admission only with the percentage you score in entrance exams.
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So, firstly choose an IIMs which you are willing to go and then refer the below provided link.
It give you the details about cutoffs and Eligiblity regarding which Institute you want to go.
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https://bschool.careers360.com/articles/iim-admission-criteria

Percentage in 10th and 12th are accorded scores which add up to the index called ‘Application Rating ( probably) or AR’ which is a composite of the two scores, graduation score, work experience score and gender diversity score or subject diversity score. Candidates are called for Pre-Admission test and interview on the basis of the AR and the CAT score. The same parameters are mostly though not always also used in the final selection.

The weightage given to AR in the selection process alongwith the CAT score as well as the weightage of 10th and 12th marks or any other parameter in the AR are decided by the individual IIMs. So you should check the respective websites for it.
As for what percentage is required, I think a basic 50–60 percent minimum requirement would be for all IIMs and some thing above 85 will give you a decent AR ( though for some IIM it can be as high as 95 %( but not higher) for the best score).

Best wishes. Thank you.