About 4000 new species of marine animals were discovered in the last two years. What is the unit rate of discovery?
To find the unit rate of discovery, we need to divide the total number of new species discovered (4000) by the number of years (2):
Unit rate of discovery = total number of new species discovered / number of years
= 4000 / 2
= 2000 species per year
Therefore, the unit rate of discovery is 2000 species per year.