Fermi Questions

Fermi Questions can be used to practice factor label (or dimensional analysis) and to practice estimation. The questions involve using estimates in calculating the answers to questions that are difficult to impossible to answer exactly. The estimates can generally give answers that compare with the "correct" answer within an order of magnitude depending on how careful the person answering the questions is in estimating each relationship.

Some resources on Fermi Questions:

Fermi Questions <http://mathforum.org/workshops/sum96/interdisc/sheila1.html

How to Solve Fermi Questions <http://www.mgt.buffalo.edu/courses/mgg/633/s1g/01_Intro/Sample_Fermi.htm >
Estimation < http://www.kidsolve.com/products/software/Estimation/>

Some examples of Fermi Questions are below:

How many MacDonald's hamburgers are eaten in the United States (or a given state) in a day? Or a year?
How many fleas are found on the dogs (or pets) in your county? City? State? The world?
How many trees are there in your state?

Read the rationale for Fermi Questions and how to solve them from the Internet resources above. Then pick one of the questions above and write a solution to it. Be sure to use your dimensions for every step. See the example below.

How many grains of sand are on a given beach?

Pick a certain volume of sand--perhaps a cubic centimeter and count (or estimate!) the number of grains of sand in it--perhaps 1000?

Then measure how deep the sand on the beach is--You might need to take several measurements and average them, but let's say 12 cm for this example.

Then measure the length and width of the beach--This one is going to be 8 meters wide by 2 kilometers long.

Calculate:

Be sure to cancel your dimensions to get the final answer!