December 4, 2023

Bobo Lin

12th Grade

Jones College Preparatory

Introduction

How many jelly beans can fill a room? How many piano tuners are there in Chicago? How long would it take you to count to one million? These seemingly impossible questions are called Fermi questions, or back-of-the-envelope questions. Fermi questions are estimation problems answered with reasonable quantitative estimates and smaller sub-questions. The purpose is not to answer the question correctly (because it doesn’t have a correct answer!) but rather to practice thinking logically and encourage communication. 

Their History

Fermi questions were named after Enrico Fermi, an Italian-American physicist known for inventing the first nuclear reactor in 1945 (SOINC). During the first detonation of the atomic bomb, Fermi was able to predict the energy released by the blast accurately. He did this by dropping pieces of paper as shock waves passed and gave an estimated 10 kilotons of TNT; the actual value was 18.6 kilotons. 10 and 18.6 might not seem close, but it was the right order of magnitude, which is the number that 10 is raised to. 

Their Significance

Guesstimation allows people to make approximations based on the information given. However, those guesstimations aren’t entirely blind. Identifying and breaking down questions is another valuable process and as a physicist, Fermi believed in breaking down complex physics problems using guesstimations. Back when advanced computational tools weren’t available in scientific fields that required quantitative calculations, guesstimations allowed researchers to decide if further calculations were needed.

Now with modern-day technologies, Fermi questions are used to train logical thinking, estimation, and analysis, especially with a need for more information. They are encouraged in physics teaching to foster better problem-solving skills before encountering complicated problems. 

Fermi questions are not only used in the classroom but also found in job interviews; tech companies are notorious for using them! As previously stated, the purpose of asking Fermi questions is not to get the correct answer but to outline a strategy and communicate how to solve a problem.

Try it Yourself 

If you’re up for challenging yourself with some Fermi questions, here are some examples from past Science Olympiad contests:

• How many 13-inch MacBook Pros would it take to weigh the same amount as a USPS delivery van?

• All-you-can-eat buffets are the best thing in the world--endless amounts of food. How many ounces of food can an average human fit in their stomach before it would (literally) explode?

• How many McDonald’s Happy Meals are sold in the US within a year?

• How many Kahoot sets have been created since the inception of the site?