Assume the population of a large city like New
York City is about 3 x 106 people, with about
2.93 people per household. Approximately 1
household in 12.3 has a piano. The piano
keyboard has about 64 notes (8 octaves) with
about 2 strings per note. A piano should be
tuned once per year (365.25 days). A piano
tuner can tune about 3 pianos per day. And,
finally, piano tuners work 252 days per year.
How many piano tuners are there in New
York City? Note: This was one of Prof.
Fermi's famous party questions. The ques-
tion has been used by others, namely Prof.
Feynman.