Imagine a library scavenger hunt. What might searchers find in the section labeled "521"? What about in the "611's"? Class groups investigate the Dewey Decimal System of numbering nonfiction books in the library. Given a number, they examine the books in their section and then label the type of nonfiction found under each grouping based on its subject matter. Individuals also reverse the process and refile books based on its number. Extension activities are also included in the packet.