Fermi problems

Fermi problems are named after the physicist Enrico Fermi,who's famous for making rapid order-of-magnitude estimations,or rapid estimations,with seemingly little available data.Fermi worked on the Manhattan Project in developing the atomic bomb, and when it was tested at the Trinity site in 1945,Fermi dropped a few pieces of paper during the blast and used the distance they traveled backwards as they fell to estimate the strength of the explosion as 10 kilotons of TNT, which is on the same order of magnitude as the actual value of 20 kilotons.One example of the classic Fermi estimation problems is to determine how many piano tuners there are in the city of Chicago, Illinois.