Summary

How many fried chicken gets sold in South Korea? How many piano tuners are there in Chicago? How many beauty salons are there in Seoul? It’s not easy to answer these questions, but with Fermi Estimation, you can get a reasonable estimation.

For example(because I’m lazy, I’ll only give one example), the population of South Korea is 50 million, and since one household is made up of 2-3 people, there are about 20 million households. Assuming that one household orders one fried chicken every week, 20 million fried chicken gets sold every week. Since one week is seven days, 20,000,000/7≈2,857,000≈2,900,000 fried chicken can be said to be sold every day. If only 10 fried chickens get sold every day, they’ll close down, but they probably can’t fry up 1,000 fried chickens, so it’s reasonable to estimate that about 40 friend chickens gets sold per chicken restaurant. If they take a day off every week, they’ll work for 6 days every week, and thus fry up 240 fried chickens per week. Since they have to fry up 20,000,000 fried chickens total per week, there can be said to be 20,000,000/240≈83,000 chicken restaurants.

According to 2019/06/03’s 한국경제신문, there are 87,000 chicken restaurants, and since about 4,000 chicken restaurants probably aren’t doing so well, this is a reasonable estimate.

Estimations like this are called Fermi Estimation, or guesstimation.

One use of guesstimation is Drake Equation, which estimates the number of alien civilization that we can communicate with.

Implication

Using Fermi Estimation, or guesstimation, you can get a reasonable estimate.

Underlying context – Background behind

Enrico Fermi, who participated in the Manhattan Project(which developed nuclear weapons), to estimate the force of nuclear explosion, threw a piece of paper after a nuclear explosion, and seeing how the distance the paper flied amounted to how far a paper would fly after explosion of 10,000 tons of TNT, Fermi estimated that the force of nuclear explosion amounts to that of 10,000 tons of TNT.

Later, in a lecture in the University of Chicago, he guesstimated the number of piano tuners of Chicago, and this is where guesstimation originated.

Notions – Key ideas

Fermi Estimation(Guesstimation) – Estimating mathematicaly

Index – Source(s)

How to Think Like Mathematicians / 피타고라스 생각 수업
02 Sometimes, Guessing Solves the Problem | Fermi Estimation / 때로는 추측이 문제를 해결한다 | 페르미 추정

Trajectory – Where I’m headed now

Not applicable