Students build and break down numbers 11–20 using base–ten blocks in this unit to develop their place-value comprehension. At the end of this lesson, students will:
- To represent a number in the range of 11–20, use base–ten blocks.
- Match numbers and displays of base-ten blocks in the range 11-20.
- Determine the number of ones and tens in the range of 11 to 20.

- How does effective communication benefit from mathematics? 
- How do patterns and relationships connect in math? 
- How can identifying regularity or repetition help with problem-solving efficiency? 
- How do we represent, compare, quantify, and model numbers using mathematics? 
- What does it mean to analyze or estimate a numerical quantity? 
- What qualifies a tool or strategy as suitable for a particular task? 
- When is it appropriate to compute instead of estimate?

- Digit: A symbol used to make a number. 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 are the ten digits we use to write numbers. 
- Ones: The place first from the right in a number. In the number 15, the digit 5 is in the ones place. 
- Place Value: The value of the position of a digit in a number. In the number 13, the 1 is in the tens place and its value is 10. 
- Tens: The place second from the right in a number. In the number 15, the digit 1 is in the tens place.

- number cards 11–20 (M-K-2-1_Number Cards 11-20)
- place-value mats (M-K-2-2_Place-Value Mat)
- Place-Value Worksheet (M-K-2-2_Place-Value Worksheet and KEY)

- Watch the students work through the activities in Lesson 2 and evaluate their comprehension of using base-ten blocks to represent numerals.
- Assess students’ place value comprehension using the Place-Value Worksheet (M-K-2-2_Place-Value Worksheet and KEY).
- Assess students' understanding of place value and the base-ten system by keeping an eye on them as they complete the Extension exercises.

Explicit instruction, modeling, scaffolding, and active engagement 
W: Explain to the class that they will be representing numbers with base-ten blocks during this lesson. We'll use worksheets and games to help with understanding. 
H: The lesson's games and activities will pique students' interest and sustain their zeal. 
E: Through exercises and games, students will represent numbers. The introduction of games and activities will follow a phased release of responsibility, moving from modeled, shared, and guided activities to partner or independent activities. 
R: Throughout the class, questions provide students the chance to consider, review, edit, and reevaluate their understanding of mathematics. 
E: Assess students' mathematical comprehension of number representation by utilizing the Formative Assessment concepts. 
T: The lesson's Extension section includes activities for Small-Group, Routine, and Expansion. 
O: The learning process will progress from modeled to shared to guided, and finally to individual practice. 

To get students ready for work with base-ten blocks, start the lesson with choral counting from 10. Say, "Count forward, starting at 10, until I tell you to stop." Stop students at the number 18. Allow students to count from 10 several times, stopping at 16, 20, and 17.

Present a long and a cube. "We refer to these as base-ten blocks." Present a cube. "It's a base-ten cube. It stands for one. Hold on for a second. It's lengthy. It stands for ten. Why does a long, in your opinion, represent ten?" (There are ten cubes in it.)

"Our number-writing system is known as the base-ten system because it is based on grouping things by tens. Base-ten blocks are useful for problem-solving and number comprehension."

Present a place-value mat (M-K-2-2_Place-Value Mat) and a set of number cards (11–20) to every child. On a place-value mat, arrange one long and five cubes. "Show 15 by placing your cards on your place-value mat." (Students demonstrate fifteen by placing one card in the tens place and the five in the ones place.) "What is the number of tens? (1) "What is the number of ones?" (5) "Check the number." (15)

Continue with additional 11–20-digit numbers. Display the base-ten blocks randomly without the mat after a few examples. As a result, students can mentally divide the blocks into ones and ten.

Reverse the previous steps. Place base-ten blocks on their place-value mats to demonstrate the numbers you write on the board, which should be 11 to 20.

Proceed with a sequence of steps utilizing number cards, written and spoken numbers, base-ten blocks, and so on. For instance,

"Use base-ten blocks to display the number 12." (One long and two cubes.)

"Show the number 13, using your number cards, with a 1 in the tens place and a 3 in the ones place." (13)

"In the number 17, which digit is in the one place?" (7) "The tenth place?" (1)

"Check the number displayed on the board." (Seventeen )

Distribute copies of the Place-Value Worksheet (M-K-2-2_Place-Value Worksheet and KEY) to every student. Assess which students understand place value and which requires more investigation by moving around the classroom, observing, and clarifying with questions.

Extension:

Routine: Students draw a number card (M-K-2-1_Number Cards 11-20) and represent the number with base-ten blocks.

Small Group: Use base-ten blocks and number cards (M-K-2-1_Number Cards 11-20). Show a number. To represent the number, students use base-ten blocks. If a student struggles to start counting at 10, they may need to use all of the cubes or swap out 10 cubes for a while.

Extension: For more practice and larger-scale extension, use the activities found in the links under Related Resources.