Lesson 10

The purpose of this How Many Do You See is for students to subitize or use grouping strategies to describe the images they see. Students may put the tens together and the ones together, which is a method for adding that will be used later in this lesson. Students may also use the 10-frames to make a new ten in order to find the total number of counters.

• Groups of 2
• “How many do you see? How do you see them?”
• Flash image.
• 30 seconds: quiet think time

• Display image.
• “Discuss your thinking with your partner.”
• 1 minute: partner discussion
• Record responses.
• Repeat for each image.

• “Did anyone see the counters the same way but would explain it differently?”

The purpose of this activity is for students to analyze a base-ten drawing used to find the value of \(37 + 26\), in which a 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

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.

• Read the task statement.
• 2 minutes: independent work time
• “Share your thinking with your partner and work together to write an explanation of what Priya did.”
• 5 minutes: partner discussion

• 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 would make sense to others?” (She showed each number clearly. She circled the tens to show she was adding them together. She 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.

• Create two separate posters that show base-ten drawings of 34 and 57. Leave space to write equations underneath the drawings.

• Groups of 2
• Give students access to connecting cubes in towers of 10 and singles.
• Read the first problem.
• 4 minutes: partner work time
• “What is the difference between how you solved \(28 + 56\) and \(27 + 44\).” (For \(28 + 56\), I added the tens first, then the ones. For \(27 + 44\) I added the ones first, then the tens.)
• 1 minute: partner discussion
• Share responses.

• Read the next problem.
• 4 minutes: independent work time
• 2 minutes: partner discussion
• Monitor for a student who starts by adding the tens and a student who starts by adding the ones for \(34 + 57\).

• Invite previously identified students to share.
• Use the prepared posters to represent each student’s thinking.
• “How are these methods the same? How are they different?” (They both add tens and tens and ones and ones. One person added ones first and the other 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 and you still get the same number.)

• Each group of 2 needs a set of digit cards from the previous center, Number Puzzles.

• Groups of 2
• Give each group a set of cards and gameboards.
• “These number puzzles have addition equations with two-digit numbers. Use the digit cards to make each equation true. Remember that you can only use each card once on a page.”

• 10 minutes: partner work time

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