McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School
Not sure if I understand your question. You should always provide clarity on the way you are doing the calculations. I strongly recommend telling the interviewer HOW you are going to calculate something before actually starting the calculations. So yes, you should tell this to the interviewer.
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as mentioned by Vlad, you can definitely mention you are using the rule of 72 - if you don’t, the interviewer will very likely ask you how you managed to calculate so quickly a compound growth. The interviewer may also ask you where the rule comes from, so be sure to review its origin, which is related to the natural logarithm.
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