# Fermi Questions Activity

2.8 based on 6 ratings
Updated on Sep 5, 2013

Great estimators are made, not born. The more practice your child gets with making estimations about the world around her, the better she'll be when it comes time to keep her math calculations in the right ballpark. Here's an activity to make your child an estimation master.

Enrico Fermi was a twentieth-century, Nobel Prize winning Physicist known for his ability to rapidly estimate calculations in his head. “Fermi Questions” emphasize determining an answer on the correct order of magnitude instead of a specific number. The goal of answering a “Fermi Question” is to make rough, educated estimates at each step of the problem and come up with a reasonable estimate to the problem. For example:

1. Fermi Question – How many pet cats are there in the U.S.?
2. Fermi Solution – There are about 300 million U.S. citizens. Most households have more than one person, let’s estimate 3 people/house or 100 million households in the U.S. I would guess 1 in 4 house holds have cats so about 25 million households have cats. Typically people have more than one cat, let’s say 2, so there are about 25 million x 2 or 50 million pet cats in the U.S.
3. Explanation – Of course you may have chosen different numbers, but in the end the answer should be on the same order of magnitude (5,000 would be too low and 5 billion would be too high!).

### What You Need:

• Pencil and paper (optional)

### What You Do:

1. Try solving the following “Fermi Questions” with your child. Use paper and pencil only if necessary, but remember, everything should be estimated. Be sure to pick round numbers (1,000 not 1,170)!
• How many pizza restaurants are in your state?
• How many cars drive down your street in a day? Year?
• What is the total amount of time all the students in your school spend studying for tests in one year?
2. Have your child think up with some of her own “Fermi Questions” and try solving them together.
3. If possible, try looking up the actual answer to the questions (use the phone book or Internet) and see how close your child’s answer is to the actual answer. Remember, you're looking for order of magnitude, not exact numbers!

The great thing about Fermi Questions is there are no right answers, only logical answers! By working through Fermi Questions, students develop logic and math skills without the fear of being “wrong.”

Lori Stewart taught eighth grade earth science and ninth grade integrated science for four years. Now, she develops science education materials.