Hello, preparation for the AIIMS MBBS in 15 days will require a basic understanding of all the concepts of science. It will be a brush up or revision of all the lessons u have studied before during the actual preparation for the test. The last 15 days prior to the examination will be revision period where you revise all the topics that you have studied already. Solving previous year's question papers of PMT and AIIMS MBBS is one of the ways of revising. Hand written notes for last minute revision are very helful. It is very important to consider that preparation for AIIMS 15 days before the examination is next to impossible. You need to study at least a year before the examination then only will u be able to revise and prepare for the exam in the last 15 days.

The cut off marks for AIIMS exam will be different for different categories and will vary each year. However,  general cut off marks for the different categories is as follows.

1. General Category: 50% in AIIMS MBBS is the minimum requirement for admission

2. OBC: 45% in AIIMS MBBS is the minimum  requirement for admission

3. SC/ ST: 40% in AIIMS MBBS exam is the minimum requirement for admission.

Hope this information helps you. 

All the best!