This lesson is optional because it does not address any new mathematical content standards. This lesson does provide students with an opportunity to apply precursor skills of mathematical modeling (MP4).

In previous lessons, students added and subtracted within 1,000. In this lesson, students use these skills to organize information about the books collected and donated during a book drive. Students organize the information in any way that makes sense to them, and decide when to add or subtract in order to keep track of how many books the school has as they collect and donate books during each month of the book drive. Students then answer additional questions about the book drive that require them to make their own decisions about the book drive.