see, in my university 70 or 72 is the highest percentage students get then how can i score more than 75......i have heard that iims do the relative shortlisting for the candidates that they have the database of all universities that how much the students of that university score.....

They have a relative short listing of candidates according to their field of study . Why they will keep the data of all the universities and check  ohh this university students gets less than 75 marks so they will have a better chance of getting admission.  It is not like that . Your university gets less marks it will not matter to them . As I said it does not only depend upon ypur graduation percentage . Many people with decent percentage in graduation gets admission into IIMS . Also they have a category wise distribution of seats .

then what i will have to get all IIM calls bcs i can't improve my score in graduation bcs of my university marking system. Max to Max 74 can be scored(including all 3 years).Should i drop a year and prepare for bba entrances 2020 so that i will be able to maintain my graduation score upto as much i want or something else......pls do help.....

No don't do that , drop in not an answer to your question , instead of it after your bachelor's  get a job and gake a work experience for 2 or 3 years which is also included in their evaluation during admissions . Work experience is the best key  for an individual to get admission in IIMS .

take *

If you took a drop then you will have to answer them during personal interview  , they will ask that why did you took a drop and what did you do in your drop year and all that . Don't be in a dilema that droping will make your career good . Be wise

i will tell them in the interview that first i did my bsc as it was my field but gradually during my grads i found my interest in administration and i thought that i should do my from the base level.....(for interviewer) (for you) bcs if i want to go for a job after my bsc as my field is bio then i won't be able to get a job which is relevant to this field.....