Estimate With Powers of 10 Practice Test

The population of the United States is about $3\times10^8$ people, and the world population is about $7\times10^9$ people. About how many times larger is the world population than the U.S. population?

A bacterium is about $2\times10^{-6}$ m long. A human hair is about $8\times10^{-5}$ m thick. About how many times thicker is the hair than the bacterium is long?