"Fermi estimate" questions are stupid most of the time. Why? Because they leave out the educated part of educated guess.
The idea is that inaccuracies in a series of educated guesses would tend to even out (though they're just as likely to compound). There is no such tendency in blind guesses, which is what most of these questions require.
The idea is that inaccuracies in a series of educated guesses would tend to even out (though they're just as likely to compound). There is no such tendency in blind guesses, which is what most of these questions require.