is it enough to if we score very well in only one subject or is it necessary to score well in all the three subjects to get qualified?

minimum marks for every subject is decided by IIT & for selection u have to score that much of minimum

mark in every subject ...if in any subject u score less then u are not eligible ...

Dear,

 it is not enough to score well in any one subject. Keep in mind, the funda of individual cut-off.

         Good Luck!!!!!1