As of early 2014, the world's population was about 7.2 billion people. the population of the united states was 317 million. the land area of a certain state is about 271,737 square miles. if in early 2014 all of the world's people were put into that state, how many people would there be in each square mile?

7,200,000,000 people
  = Either 26,496 or 26,497 people per sq.mile.
271.737 sq. miles 

Since the data that is going into the equation is "about 7.2 billion people", you have to make a decision on how you round.  I would round down as 26,496 people would for sure be on each sq. mile.   You can't break people up into decimals or fractions, so pick a number. 

Athe rate increases as income increases