The object of this quiz is to adjust each circle's diameter so it splits the circle's population as evenly as possible. When you click Start you will be shown a marker on a random US census tract (there are over 80K census tracts in the US). Also you will see an circle between 200 and 500 miles radius. Adjust the diameter by rotating it using the endpoints, trying to split the halves into equal populations. Then click submit. You are scored on how close you have split the circle into 50% population in each half. Circle population is tallied by totaling all census tracts (small census areas of average 4K population) within that circle.
NOTE - population in Canada and Mexico is NOT counted at all, only US population within the circle.
Quiz Takers 
It would be fun to have a US Largest Cities – Choose States
Great quiz-
Played this quiz with a few different configurations. I haven’t been able to get one of my scores saved yet. Do you know what may be causing the issue?
They save under each configuration. So you will only see your score displayed playing a configuration you already have done.