Next up was Rohit Dhawan. Another Googler, he had that very well put together and confident air of someone who felt he had mastered his field of work (he was a Penn grad, of course). His angle was analytical ability, and he asked me a variant of that legendary Enrico Fermi brainteaser about piano tuners in Chicago. His variant was to estimate the number of planes in the sky at any given moment. It required nothing more than some rough base assumptions about number of airports and flights per day, and then some dimensional analysis that got us within an order of magnitude of reality, and we
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