Side note: I watched a once-coworker give a 30 minute lecture to high school students on how to do these giant puzzle/estimation types. His trick was to take t

Side note: I watched a once-coworker give a 30 minute lecture to high school students on how to do these giant puzzle/estimation types. His trick was to take the geometric mean of reasonable min/max bounds at different stages of the estimation. Example question: How many flights occur in America in a day? You can start from the bottom, with an estimate of the number of people who fly, then the number that can fit in a plane, et cetera. Alternatively, you can start from the top at the number of airports and their flight capacity. With a bunch of sqrt(minbound*maxbound) and reasonable guessing, the students (via groupthink) ended up with two roughly matching estimates that were within an order of magnitude.