In 1900 ,a certain country's population was 72,028,751 and its area was 2,967,929 square miles. In 1980 ,the country's population was 276,948,879 and its area was 3,730,271 square miles.
a. Find the population density of the country, to the nearest tenth, in 1900 and in 1980.
b. Find the percent increase in population density, to the nearest tenth of a percent, from 1900 to 1980.