The purpose of this activity is for students to solve a new type of story problem—Compare, Smaller Unknown. Students represent and solve the problem in any way that makes sense to them. 

Monitor for and select students with the following approaches to share in the Synthesis:

• Draw or build one tower of 14 cubes and remove 4 cubes.
• Draw or build two towers of 14 cubes and remove 4 cubes from one of the towers.
• Draw or build one tower of 14 cubes, draw or build a second tower with 4 fewer cubes than the first tower.

When sequencing student approaches, consider inviting students to share from the most common approach to the least common approach used during the activity. This sequence will help students make sense of and connect different approaches that can be used to represent and solve a Compare, Smaller Unknown story problem. Aim to elicit both key mathematical ideas and a variety of student voices, especially students who haven't shared recently.

• Invite previously selected students to share in order from the most common approach to the least common approach. Record or display their work for all to see.
• Connect students’ approaches by asking:
  • “What is the same about how they solved the problem? What is different?” (They all found Priya’s bracelet is 10 cubes long. The first way showed 1 tower of cubes. The other ways showed 2 towers of cubes. The first two ways took cubes off of a tower. The last way added cubes to make Priya’s bracelet.)
• Connect students’ approaches to the learning goal by asking:
  • “Where do you see Han’s bracelet in their work? Where is Priya’s bracelet?” (In the first way they started with Han’s bracelet, took off 4 cubes, and ended with Priya’s bracelet. In the other ways, we see Han’s and Priya’s bracelets at the same time.)
  • “How did each student use Han’s bracelet to find the length of Priya’s bracelet?” (The first broke off the 4 fewer cubes from Han’s bracelet to make Priya’s bracelet. After the second person took away the 4 cubes, they looked at Han’s bracelet to check that Priya’s bracelet had 4 fewer cubes. The last person kept adding cubes to Priya’s bracelet until they saw it had 4 fewer cubes than Han’s bracelet.)

The purpose of this activity is for students to make sense of and solve a Compare, Bigger Unknown story problem. The numbers are intentionally the same as the problem in the previous activity. During the Lesson Synthesis, students analyze a representation and describe how it can represent both story problems (MP8).

• Invite previously identified students to share what they noticed.
• Invite students to share how they solved the problem.

The purpose of this activity is for students to learn Stage 3 of the Write Numbers center. Students choose to count forwards or backwards by starting at either of the numbers on a gameboard. Students take turns counting by 1 and writing the next one, two, or three numbers. The player who writes the last number on the board wins.

Consider laminating gameboards or placing them in sheet protectors so they can be used multiple times.

• Play one round with the class. Discuss how they decide whether to write one, two, or three numbers.