Lesson 26

The purpose of this warm-up is to introduce the idea of a book sale, which will be useful when students work with this context in a later activity. While students may notice and wonder many things about these images, the range of and prices and types of books are the important discussion points.

• Groups of 2
• Display the image.
• “What do you notice? What do you wonder?”
• 1 minute: quiet think time

• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Share and record responses.

• “What are some things we have to think about if we plan a book fair for our school?” (The different types of books we sell and have to order, the cost of the books for us, the amount to charge for each book, the number of people who come to the fair, and the number of books that we sell.)

• Groups of 2
• “When a school plans a book sale fundraiser, the school orders books from the publisher, or bookseller, for a certain price. Then the school sells it for a different price at the book fair.”
• “Let’s imagine the school buys a book for \$10. Should they sell the book for more or less than \$10 at the book fair? Why?” (More if they want to make money from the sale.)
• “This is called the mark-up price. For every book they sell, the bookseller will get \$10 and the school keeps the amount they added. The amount they add is called the profit.”

• 1 minute quiet think time
• 5 minutes: group work time
• Monitor for students who consider the profit per book in their justifications.

• “What is a reasonable mark-up price?”
• “What do you need to consider when deciding a mark-up price?”

In this activity students plan a school book fair. They choose the types of books to order and the cost for each type of book. They also estimate how many people might come to the book fair and how much money the school might raise through the book sale.

Students will have to make many assumptions in this activity: how many people are coming, how many books each person will buy, and how much to add to the price of the book, to name a few. When students are explicit about assumptions, they model with mathematics (MP4).

• Groups of 2
• “In this activity, you’ll plan a book fair. The table shows the price list of each type of book from the publisher.”
• “Sometimes when we plan something like a book fair, we make assumptions. Assumptions are things we think will be true based on our experiences, but they might not always be. For example, we can make assumptions about who might come to the book fair.”
• “Who might come to the book fair and buy books?” (students, parents, grandparents, friends)
• As you plan the book fair, think about other assumptions you make, how they affect the book fair, and how to communicate them in your work.

• 1–2 minutes: quiet think time
• 10–12 minutes: partner work time
• Monitor for students who:
  • Select the types of books based on the kinds of attendees. For example, they select history books because that is something parents want and chapter books which are preferred by students.
  • Make assumptions about the number of attendees and the number of each type of book sold.

• Invite students to share their book sale plans.
• Invite students to share their assumptions.
• “Why did you make these assumptions?” (There are 600 students, so I thought that maybe only half would come since that is usually what happens. Since the school wants to make a profit, but also make the books affordable, the mark-up price is only one more dollar than the list price.)