Hello Ansalna,

Kepp these points in your mind-

• Nothing is defined or determined.
  
• Paper patterns change every year.
• Number of takers change every year.
• Relative toughness changes every year.
• Relative smartness of students increase so papers are more easily solved every year.
• Most IMPORTANTLY Questions change every year.

So to be on safe side scoring atleast 100/180 will fetch you any of the lower IISER ,scoring more than 130 can fetch you the top IISERs like IISER Pune and Kolkata.

Hope this Helps.

Stay connected for further queries.

All the Best!