An Urban Density Model Is a Formula That Relates the Population

Multiple Choice

An urban density model is a formula that relates the population density D ( in thousands/ mi ² ) to the distance x (in miles) from the center of the city. The formula for the central density a and coefficient of decay b has been found to be appropriate for many large U.S. cities. For the city of Atlanta in 1970, a = 5.5 and b = 0.10. At approximately what distance was the population density 2,800 per square mile?

A) 2.9 mi
B) 6.8 mi
C) 14.7 mi
D) 9.1 mi
E) 62.3 mi