Hello!

ItsI not just the number of right questions that matter, but the number of wrong questions too. If your aim is to get selected, be very sure while marking answers. There is 1/3 negative marking for every wrong answer and +1 for every right answer. Don't rush to answer everything. Mark only those questions which you are absolutely sure about or take a well calculated guess. 

There is no limit of "minimum" answers required and the cutoffs vary every year. Usually the level of AIIMS exam is high and sometimes answering less questions, but answering them correctly can fetch you a high percentile. All the best!