The purpose of this activity is for students to analyze a base-ten drawing used to find the value of . The student adds tens and tens and ones and ones. Students make sense of the method used, and consider what made the representation of this method easy for them to understand. This will be helpful when students are asked to represent their addition methods in a way that makes sense to others.

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

• Invite students to share how they interpreted Priya’s work.
• “Representing our methods in a way that makes sense to others is very important. How did Priya make sure her representation made sense to others?” (Priya showed each number clearly. She circled the tens to show she was adding them together. Priya circled 10 ones to show she made a new ten. She labeled the new ten and the extra ones.)

The purpose of this activity is for students to consider the associative and commutative properties when adding 2 two-digit numbers. In the first two problems, a base-ten drawing and an expression representing adding tens and tens or ones and ones is given as the first step. Students determine the next steps and find the sum. When students decompose the 2 two-digit numbers into tens and ones, combine the tens and ones, and then find the total, they use their place value understanding to make sense of addition (MP7).

During the Activity Synthesis, the teacher records students’ thinking using premade posters of 34 and 57 as tens and ones. Students discuss that you can add the parts of the numbers in any order.

• Invite previously identified students to share.
• Use the prepared posters to represent each student’s thinking.
• “How are these methods alike? How are they different?” (They both add tens and tens and ones and ones. One person added ones first, and the other person added tens first. They got the same answer whether they added tens first or ones first.)
• “Why do they both work?” (You can add in any order. You still get the same number.)

• Display a gameboard.
• “Which equation can you fill in first?”