The problem is that the interviewer asks for a number. If the question was phrased as "How would you go about finding out the GoogleAds B2B revenue in Italy for

The problem is that the interviewer asks for a number. If the question was phrased as "How would you go about finding out the GoogleAds B2B revenue in Italy for 2017, which tools and methods would you use", I'd totally go for that question. The reason is that to many people (myself included) your answer above is nonsensical. “With ~50M people capable of clicking ads, and assuming they click one ad a day at 20cnt CPC, it would be around 3.6bn. I think my assumptions are on the high side, but order of magnitude is probably correct” Where did the "people capable of clicking ads" 50M estimate come from? Why one ad a day on average? Why not 0.2? Or 15? Why 20c CPC and not 0.001 euro cent? Why not 1USD? I'm all for "first-principals based structured thinking" but asking someone to demonstrate that by generating a rudimentary formula, that won't survive any contact with reality, and populate it with almost completely random values, seems like a weird way to go about it.