Be an Estimation Sensation

Great estimators are made, not born. The most 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!).

Step 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)!