During my round 2 case interview with an associate partner at McKinsey, I was asked to calculate breakeven quantity for a go/no-go kind of business case. I explained all the steps before calculating, wrote things down and shared what I found at the end with some additional information. Then, a strange thing happened: the interviewer took the paper that I did all my calculations on and checked my answer and went through her papers in silence for around a minute and a half. Once she finished checking, she gave it back and carried on the interview as usual. The answer that I found seemed reasonable and made sense. I was wondering if this is common in round 2 interviews and what it really means. I will appreciate any kind of help/advice to prepare for my next interview to avoid such a situation as it affected the pace and the rhythm of the interview.