The purpose of this activity is for students to solve a story problem in a way that makes sense to them. The goal is to elicit and highlight the different ways students use diagrams and other representations when solving a story problem. They solve a Compare, Difference Unknown problem within 50 that requires composing or decomposing a ten if students add or subtract by place. Students may represent or solve the problem with any approach that makes sense to them.

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

• Represent the problem as a comparison using a tape diagram or rows of connecting cubes or base-ten blocks.
• Add or subtract by place to find the unknown using base-ten blocks or a base-ten diagram.

The approaches are sequenced from ways students may use representations to make sense of the problem to ways they may use representations to calculate the value of the unknown. This discussion helps students consolidate the ways they have used diagrams in previous lessons to solve problems and the ways they have used base-ten representations to add and subtract within 100. Aim to elicit both key mathematical ideas and a variety of student voices, especially students who haven't shared recently.

• Invite previously identified students to share in the given order. Record or display their work side by side for all to see.
• Connect students' approaches by asking:
  • “¿En qué se parecen estas representaciones del problema? ¿En qué son diferentes?” // “How are these representations of the problem the same? How are they different?” (They both show the amount of Diego’s seeds and Jada’s seeds. One representation shows the problem and helps you see the bigger amount, the smaller amount, and the difference. The diagram that shows tens and ones helps you see how they added or subtracted tens and ones.)
• Connect students’ approaches to the learning goal by asking:
  • “¿Cómo nos ayuda cada tipo de representación a resolver el problema?” // “How does each kind of representation help you solve the problem?" (The tape diagram helps you make sense of the numbers in the problem and figure out what you need to find. The base-ten diagram helps you find the unknown value.)

The purpose of this activity is for students to solve different types of story problems within 50 that may require composing or decomposing a ten when adding or subtracting by place. Students are encouraged to solve the story problems in a way that makes sense to them. The Synthesis focuses on sharing the ways students made sense of and solve a Compare, Smaller Unknown problem.

Monitor for a variety of different ways students use drawings, diagrams, or equations to make sense of or solve the problems for sharing in the Lesson Synthesis. Look and listen for examples of ways students make sense of what they need to find, such as using a tape diagram or base-ten blocks, before they use methods to calculate unknown values (MP1).

• Invite previously identified students to share their diagrams and labels.
• If students do not use tape diagrams to show the last problem, but represent their thinking using visually similar ways (for example, placing a row of base-ten blocks above another row of base-ten blocks), record these methods using a tape diagram.
• Consider asking:
  • “¿Cómo les ayudó su representación a entender el problema-historia?” // “How did your representation help you understand the story problem?” (It helped me show what was happening with the seeds in the story. It helped me show the different groups of seeds and what I needed to find.)
  • “¿Cómo les ayudó su representación a resolver el problema-historia?” // “How did your representation help you solve the story problem?” (It helped me see what I needed to find and helped me think about whether I wanted to add or subtract to find the unknown value.)