Mental calculation?

Stern Stewart Case: Sportliches Wachstum
New answer on Mar 08, 2020
2 Answers
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Anonymous A asked on Mar 05, 2020

Would the interviewer expect mental calculations to solve this case? If so, would it be fine to work with rounded numbers?

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replied on Mar 05, 2020
McKinsey Senior EM & BCG Consultant | Interviewer at McK & BCG for 7 years | Coached 300+ candidates secure MBB offers


This is one of the many nonsense-myths flying around! MBB interviewers NEVER expect mental math! The only thing expected is that you can perform calculations in a clear and correct way, while taking along (!!!) the interviewer! This means that, apart from super easy calculations, you should always do rock-solid written calculations! NOBODY is interested in your mental math skills! It is NOT a relevant category in assessing a candidate's performance, and every MBB interviewer is explicitly trained on that. The interviewer will assess you on whether you are accurate and clear!

In the extreme, very fast mental calculations are even very detrimental to a candidate's performance. Here's why: The interviewer will always assume that the way you behave in an interview is indicative of how you would behave with a client. So if you do all sorts of complicated math stunts in your head - guess what? You become extremely difficult to follow for the client! And at that point it becomes completely irrelevant whether your result is correct or not. If it is hard to follow your analysis, then your performance is poor. End of story.

Cheers, Sidi

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Anonymous A on Mar 05, 2020
Thank you very much for your answer. Do you think it would even be allowed to work with a calculator as the numbers of this specific case are really large and not even.
Sidi on Mar 05, 2020
Not in traditional 1-on-1 interviews. In written cases it varies between firms.
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replied on Mar 08, 2020
BCG |NASA |20+ interviews with 100% success rate| 120+ students coached |GMAT expert 780/800 score


The only thing that is mandatory during the interview is to not do any mistake in your calculations.
Having said that, doing some mental calculation could really impress your interviewer, but do it only if you are sure of the result. You can even give a result doing fastly the mental calculation with rounded numbers and then write down the calculation with the exact numbers.


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McKinsey Senior EM & BCG Consultant | Interviewer at McK & BCG for 7 years | Coached 300+ candidates secure MBB offers
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