The purpose of this activity is for students to make sense of the first step of addition methods and then finish finding the sum. They write equations to represent their thinking. In the Activity Synthesis, students have opportunities to share how they represented a method with equations and connect the representations using their understanding of place value (MP7).

• “¿Qué hizo Lin (o Han) primero? ¿Cómo podrías usar cubos encajables para mostrar lo que hicieron?” // “What did Lin (or Han) do first? How could you show what they did with connecting cubes?”
• “¿Qué tienen que hacer después? ¿Cómo lo sabes?” // “What do they need to do next? How do you know?”

• Invite previously identified students to share their equations for Lin's work and then Han's work.
• “¿En qué se parecen estas ecuaciones? ¿En qué son diferentes?” // “How are these equations alike? How are they different?” (They both got the same sum. They both add tens and ones. The first one breaks apart both numbers and adds tens and tens and ones and ones. The second one starts with 54 and adds the tens then the ones.)

The purpose of this activity is for students to find the sum of 2 two-digit numbers and represent their thinking with equations. Students then orally explain their steps to a partner and how the equations they wrote match their steps. Partners listen and then practice restating what they heard their partner say. Restating what a partner has said helps ensure students listen for understanding as their partner explains their thinking. Students have multiple opportunities to explain their thinking and the thinking of a partner and revise their language for clarity (MP3, MP6).

This activity uses MLR8 Discussion Supports. Advances: listening, speaking, conversing.

• “¿Qué les pareció lo más difícil al intentar expresar de otra manera las ideas de su pareja? ¿Qué les ayudó a entender las ideas de su pareja y a decirlas con otras palabras?” // “What was most difficult about restating your partner’s thinking? What helped you make sense of your partner’s thinking and restate it?”