Hi,
There is no fixed duration of the interview. It would however be not less than 20 minutes, and usually not more than 45 mins. Mine lasted for about 30 mins.
Extempore can be for 8-10 mins also as the speaking length would depend on the knowledge of the topic one would choose. After your extempore, panel will discuss regarding your view points and that would be about 7-10 mins more, but not certain. Different people had different timelines last time based on the panel they went to. My extempore went for about 5 mins, followed by discussions for another 5-6 mins. I used a strategy of writing down the points, and went ahead in that sequence to explain my stand to the panel. That keeps the thought process steady and helps to get over the initial nervousness..

There is no sacrosanct rule regarding decision based on extempore, but yes, from what I can make out based on my experience and speaking to other successful candidates, it does play an important part. The panel will check one's ability to handle a topic in short notice, how you can analyse and put up your points in a logical and coherent manner. But please dont panic if the extempore doesn't go well as per your expectations, you never know what the panel's opinion is..

... go ahead confidently with the balance part of interview.
Just be calm composed and honest about your answers, and everything will fall in place. It would be a conversational tone, not a grilling interview, just enjoy the process and you would do great.
Best of luck
Warm regards
SlavaKing
Could someone please comment on the following aspects of IIM-A interviews ?
- Is the duration fixed at ~30 mins? I have seen multiple posts and advice to stop the extempore b/w 15 min and 20 min mark. Although, this seems very unreliable advice
- Someone shared that the panel judges mostly on the extempore topics. And an initial decision is made in the first 10 minutes. How true is that?