You're right on the fact it's a stupid question you have to look up, and brings barely any value to the interview (I think in a follow up version he removes the

You're right on the fact it's a stupid question you have to look up, and brings barely any value to the interview (I think in a follow up version he removes the question). Regarding not recognizing your own ignorance, I think you definitely have to mention in your answer that really you are making up all the numbers and just tackling it in the first logical way you came up with.