Lesson 10
Write Twodigit Numbers
Warmup: Notice and Wonder: Same Digit, Different Place (10 minutes)
Narrative
The purpose of this activity is for students to see the connection between baseten diagrams and written numbers. In the synthesis, students consider the relationship between numbers with the same digit in different places. Students also observe that the singledigit number has no tens.
Launch
 Groups of 2
 Display the image.
 “What do you notice? What do you wonder?”
 1 minute: quiet think time
Activity
 “Discuss your thinking with your partner.”
 1 minute: partner discussion
 Share and record responses.
Student Facing
What do you notice?
What do you wonder?
7
70
17
71
Student Response
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Activity Synthesis
 “How are 7 and 17 the same and different?” (They both use the digit 7 but only 17 has 1 ten. Seven has no tens.)
 “How are 7 and 70 the same and different?” (7 is a onedigit number and 70 is a twodigit number. They both have a 7 as a digit. 70 has 7 tens. 7 has 7 ones.)
 “How are 70 and 71 the same and different?” (Both have 7 tens, but 71 has 1 one instead of 0 ones.)
Activity 1: Write Numbers to Match BaseTen Representations (15 minutes)
Narrative
The purpose of this activity is for students to produce written numbers for a given quantity represented in different ways. Some representations show the tens on the left and others show the ones on the left. Students must attend to the units in each representation and the meaning of the digits in a twodigit number, rather than always writing the number they see on the left in a representation in the tens place and the number they see on the right in a representation in the ones place (MP6).
Supports accessibility for: Attention, SocialEmotional Functioning
Required Materials
Materials to Gather
Launch
 Groups of 2
 Give students access to connecting cubes in towers of 10 and singles.
Activity
 Read the task statement.
 “You will work on your own to start. When you and your partner are finished, compare your work.”
 5 minutes: independent think time
 3 minutes: partner discussion
Student Facing
Write the number that matches each representation.

1 ten 4 ones
Number: ____________

Number: ____________

9 tens
Number: ____________

\(20 + 5\)
Number: ____________

Number: ____________

\(7 + 40\)
Number: ____________

2 ones 8 tens
Number: ____________

Number: ____________

\(1 + 40\)
Number: ____________

Number: ____________
Student Response
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Activity Synthesis
 Invite students to share the twodigit number that matches each representation and explain how it matches.
Activity 2: Introduce Write Numbers, Numbers to 99 by 1 (20 minutes)
Narrative
The purpose of this activity is for students to learn a new center called Write Numbers. Students write a twodigit number in each space on a gameboard. They take turns writing the next one, two, or three numbers in the sequence. The player who writes the last number on the board wins. Students may choose to count forward or backward.
Advances: Speaking
Required Materials
Materials to Gather
Materials to Copy
 Write the Number Stage 1 Gameboard
Required Preparation
 Put each gameboard in a sheet protector.
Launch
 Groups of 2
 Give each group a gameboard and a dry erase marker.
 “We are going to learn a new center called Write Numbers.”
 Display the gameboard.
 “You and your partner will practice writing numbers. You will fill in the number path on the gameboard. You can decide to start with the smaller number and count forward, or start with the larger number and count backward. On each turn, you can decide whether you would like to write one, two, or three numbers on the gameboard. The person who writes the last number on the board is the winner.”
 Demonstrate playing one round with the students.
 “Now you will play with your partner.”
Activity
 10 minutes: partner work time
Activity Synthesis
 “What patterns did you see as you wrote numbers?” (The ones place goes up by one each time until you get to 9. Then the tens place changes by one, and the 0–9 pattern repeats.)
Lesson Synthesis
Lesson Synthesis
“Today we wrote twodigit numbers. Clare counted a collection of seventytwo objects. This is the number she wrote. Give a thumbs up if you agree and a thumbs down if you disagree.”
“What advice do you have for Clare about writing numbers that have tens and ones?” (When writing tens and ones there are only 2 digits. The first digit tells the number of tens and the second digit tells the number of ones. There is no 0 in 72, even if it sounds like there should be.)
Cooldown: Write Numbers (5 minutes)
CoolDown
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