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Your friend's percentile is 79 It means 79% student of the Total student appeared for the Exam are Behind him  Therefore 21% students of the Total students appeared for the exam are Ahead of him, Therefore his calculated rank is 183638

His Rank would change Either Your Percentile Score is Increases in the next attempt or Number of Student increases in the Next attempt If the Number of Student Increases to 1400000 and his percentile remains same then his New rank would be 294000

As per his current Performance, He may be eligible for JEE Advance But the final cut off will be released once the JEE Main April gets Over

If Your Percentile Score Increases in the Next attempt Then Your Rank would Be calculated By the Following Formula

 (100 - your total percentile score (Higher of two)) X Student appeared in JEE Main/100

 At this rank It is Not possible to get admission into any NIT, Please try better in the next attempt of JEE Main

 You should Try to get more than 98 percentile for NIT

Hope this Helps All the Best