This lesson is optional because it does not address any new mathematical content standards. This lesson provides students with an opportunity to apply precursor skills of mathematical modeling (MP4). In this lesson, students build on their previous understanding and experiences with decimal numbers to plan a school book fair. They consider different categories of books to order and the sale price of the books. They estimate the number of people likely to attend the fair and approximate the amount of money the school can make from sales.

School book fairs are common events in many schools and are often used as fundraisers. Depending on how familiar students are with this context, an introduction may be necessary.