Bring Your Questions for the Street-Fighting Mathematician

How many Starbucks are in New York City? How many light bulbs on one city block? How many airplanes are approaching Chicago O’Hare Airport right now?
This sort of question, particularly familiar to anyone who has ever interviewed for a management-consulting job, requires a form of problem-solving that’s not really taught in math or economics classes: educated guessing. They’re also the kind of questions at the center of a new book by Sanjoy Mahajan, a physicist and associate director of M.I.T.’s Teaching and Learning Laboratory.
Street-Fighting Mathematics espouses a different kind of problem-solving than many people are accustomed to, one that’s attuned to real-world problems and requires less rigor than usual (as Mahajan puts it: “rigor leads to rigor mortis”). In a recent interview with The Chronicle of Higher Education, Mahajan estimated the amount of money in a Brinks truck and the annual state budget of Delaware.
Mahajan has agreed to field questions from Freakonomics readers, so let them fly in the comments section below and, as always, we’ll post his answers in short course.