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. As students choose items for their wish list, they have more options than those shown in the Warm-up.

Consider having students look up costs of additional items they would like to include in their wish list, using resources such as websites (with help from an adult), book-fair flyers, or supply catalogs if available. When students consider assumptions about information not given in a situation, model a situation, using a representation such as an equation, and report on conclusions and reasoning, they model with mathematics (MP4).

• Invite previously selected students to share.
• “How did you decide what would be on your wish list?” (I chose a box of markers at the end because we had spent $995 and only had $5 left. I chose the aquarium with fish because I thought it would be good to have a class pet. I chose a set of books about nature, because we already have a lot of storybooks, but need more information books.)
• “Did your actual cost go over $1,000 or stay under?” (We stayed just under budget. We went a little over budget, but then took something off the list so we stayed under $1,000.)
• “How did rounding affect whether your actual costs were over $1,000 or under $1,000?” (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.)

The purpose of this activity is for students to present their selections from the previous activity to another 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. When students report on conclusions and reasoning, they model with mathematics (MP4).

• Invite groups to share how their strategies compare 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.