What happens if in an Investment Banking interview you’re asked a technical question that you don’t know how to answer? Acknowledge you don`t know the answer, but if you understand elements of the question, proceed to talk about those. For example, if the interviewer asks if you are familiar with a particular valuation methodology, and you don`t know that one but you do know some others, you should say that you`re not familiar with that particular methodology, but you have calculated EBITDA multiples and P/E ratios, and you used them for the following purposes.