Hi Ujwal,
Your marks in class 10th and 12th are considered at the time of final merit list in IIMs and other top B-schools for admissions. However, you must have at least 50% marks in graduation from a recognised board in order to be eligible to apply for CAT exam. To know more about CAT 2018 Eligibility, explore the link given in the text.
Hope that's helpful. All the best.
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