Lesson 21

The purpose of this warm-up is to elicit observations about school supplies in different categories and with varying prices, familiarizing students with the context for upcoming work. While students may notice and wonder many things, focus the discussion on the large selection and wide range of prices.

• Groups of 2
• Display the table.
• “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.

• “If you had to pick one item from this list for our classroom, what would you pick?”
• “What is one other thing you would like to get for our classroom that is not on this list?”
• 30 seconds: quiet think time
• Share and record responses.

The purpose of this activity is for students to make a wish list of items for the classroom with a $1,000 budget. As they make their selections, they keep an estimate of the total by rounding, and use estimation and addition strategies to remain within the budget. To make their wish list, students use a supply list that is longer than shown in the warm-up.

• Groups of 2
• “Imagine our class got a donation of \$1,000 to spend on anything we’d like from the list.”
• “Today you will get to decide how to spend \$1,000. As you make your choices, estimate or round to keep track of your total until you get close to \$1,000.”

• 2 minutes: independent work time
• 10-12 minutes: partner work time
• Monitor for a variety of addition strategies students use to keep track of their budget.
• Monitor for students who:
  • round to the nearest ten
  • round before multiplying or round after multiplying the quantity
  • revise their list if they were under or over budget

• Invite previously selected students to share why they made revisions to their wish list.
• “Turn and talk: How did you make your choices?” (Rationale can go beyond the cost of items, such as students liking a specific item or stating the need for an item.)
• Share responses.
• “Did your actual cost go over the $1,000 or stay under?”
• “Did rounding affect whether your actual costs were over or under $1,000? If so, how?” (My rounding made my actual cost stay under because I rounded up a lot when I estimated the cost. My actual cost went over because I rounded down a lot.)

In this activity, students present their selections to a partner group. They explain their choices and compare how much money they plan to spend in each category. They make comparisons using “how much more” and “how much less” statements.

• Groups of 2
• “Now, share your wish lists with another partnership. Take turns sharing what you chose and explain the choices you made.”
• Pair each group with another group to share.

• 10-12 minutes: small-group work time
• Monitor for “more than” and “less than” language when students make comparisons.

• Invite groups to share how their strategies compared to those of their partner groups.
• Invite partner groups to share their comparisons with the whole class using “how much less” and “how much more” statements.