The number of visits to public libraries increased from 1.2 billion in 1998 to 1.3 billion in 2002. Find the average rate of change in the number of public library visits from 1998 to 2002.
+181 (1.3 billion - 1.2 billion) / (2002 - 1998)
= 1000 million / 4
= 250 million visits per year
