## Building Sets of 17 and 18

Pre-K-2
1

Students construct sets up to size 18, write the numerals 17 and 18, and model 17 and 18 with bean sticks, cubes, and ten frames.

To assess prior knowledge, gather students in a circle. Distribute a numeral card with a number between 1 and 18 on it, turned face down, and a resealable plastic bag containing a set of 1 to 18 cubes to each student.

Ask students to compare their numeral card with the cubes in their bag to determine if they match. If the students’ numeral cards do not match the cubes in their bag, have each student display his or her card (taking turns one-by-one) to the other students in the class and ask them to trade their bag for one with the number of cubes that does match the numeral card.

If time permits, you might wish to have students verify that the bag of cubes that is traded does match the numeral card of the student displaying the card.

To begin the lesson, show the numeral 18 and tell students to clap their hands 18 times, counting aloud as they do so. Call on students to name other actions to do 18 times and have the class do them and count each time.

Give each student connecting cubes and the Ten Frames Activity Sheet.

Have each student count out 18 connecting cubes and ask them to show 18 in the ten frame. Then ask how they would model 17 in the ten frames.

Ask students to divide 18 cubes into two groups in as many ways as they can. Ask them to record the ways. After they have had time to work, encourage them to share how they divided the cubes. Encourage them to make statements, such as "I made a set of 7 and a set of 11 from 18 cubes." Record each decomposition where all the students can see.

Next, open the Adjustable Spinner interactive. Demonstrate for students how to create and use the spinners.

You may use only one computer for the demonstration or have students work together on multiple computers. This interactive may also be used on tablets.

Create an 11-part spinner by entering the numbers 10 to 20 in the left column. As you enter each number, call on a volunteer to choose a color for that section of the spinner. Then activate the spinner. Ask students to say the resulting number aloud and make a tower with that many connecting cubes, using ten of one color and completing the model with another color. Call on a volunteer to tell how many of each color he or she used to make the tower.

In the example below, the student might say, "I used 10 blue and 8 red cubes to make my tower of 18."

It may reinforce learning to repeat this activity several times using different numbers and choosing a different child to activate the spinner each time. Ask students to model each number that is selected with bean sticks.

Ask students to add models of 17 and 18 to their bean stick record sheet, previously started in this unit. Collect these sheets for use in the next lesson.

### Reference

Burton, Grace M. Towards A Good Beginning: Teaching Early Childhood Mathematics. Menlo Park, CA: Addison-Wesley, 1985.

• Connecting cubes
• Resealable plastic bag
• Crayons
• Index cards
• Glue
• Bean sticks
• Paper
• Numeral Cards (photocopied on cardstock)
• Ten Frames Activity Sheet
• Computers or tablets with internet access

Assessment Option

The observations you have recorded throughout the unit will be useful as you discuss student progress with other adults who work with your students. Your observations will also be useful in focusing conversations with parents during conferences. You can record such observations on the Class Notes recording sheet.

Extensions

Rather than using an extension, move on to the last lesson in this unit, Building Sets of 19 and 20.

Questions for Students

1. Show me a group of 18. Repeat with 17.
2. Make a tower of 17 and a tower of 18. Which tower has more? How can you tell? How many more?

[The tower of 18 has 1 more.]

3. Count out 18 connecting cubes. Now make two groups with those connecting cubes. How many are in each group? Can you make two groups with 18 connecting cubes in another way? Can you make two groups with 18 in five different ways?

[Answers may include: 10 and 8, 9 and 9, 11 and 7, 12 and 6, and so on.]

4. What do you need to do to change a group of 18 to a group of 20? What do you need to do to change a group of 18 to a group of 10? Show this using ten frames. Show this using bean sticks. Explain what you did.

[Add 2 more; take away 8.]

5. What number comes after 18? Before 18?

[19; 17.]

Teacher Reflection

• Are there students still unable to count out up to 18 objects? What should I do at this time to help them reach this goal?
• Which students are able to identify the numerals to 18? Which students are not yet able to count rationally to 18? What experiences do they need next?
• Which students were not yet able to write the numerals up to 18? Which numerals are the most difficult for them?
• Which students are able to compare other sets to sets of size 18? Which students are not yet able to do this? What learning activities should I plan for them?
• What adjustments will I make the next time I teach this lesson?

### Building Numbers Up to 10

Pre-K-2
Students construct sets of numbers up to 10, write the numerals up to 10, and count up to 10 rationally. They use ten frames and also make bean sticks.

### Building Sets of 11 and 12

Pre-K-2
Students use bean sticks, connecting cubes, and ten frames to construct sets of 11 and 12, record them, and compare them.

### Building Sets of 13 and 14

Pre-K-2
Students construct and identify sets of size 13 and size 14. They compare sets to sets of size 13 and size 14, and record the number in the sets. They decompose a set of 13 and a set of 14 in several ways.

### Building Sets of 15 and 16

Pre-K-2
Students explore the numbers 15 and 16. They make and decompose sets of size 15 and size 16, write the numerals 15 and 16, and compare other sets to sets of size 15 and size 16.

### Building Sets of 19 and 20

Pre-K-2
Students explore sets of 19 and 20. They count up to 20, construct and decompose sets up to 20, and record the decomposition.

### Learning Objectives

Students will:

• Construct and decompose groups of 18 objects.
• Identify and write the numerals 17 and 18.
• Compare sets to sets of size 18.
• Record the number of objects in a group of size 17 and size 18.

### NCTM Standards and Expectations

• Connect number words and numerals to the quantities they represent, using various physical models and representations.
• Count with understanding and recognize "how many" in sets of objects.
• Develop a sense of whole numbers and represent and use them in flexible ways, including relating, composing, and decomposing numbers.

### Common Core State Standards – Mathematics

-Kindergarten, Counting & Cardinality

• CCSS.Math.Content.K.CC.A.1
Count to 100 by ones and by tens.

-Kindergarten, Counting & Cardinality

• CCSS.Math.Content.K.CC.A.2
Count forward beginning from a given number within the known sequence (instead of having to begin at 1).

-Kindergarten, Counting & Cardinality

• CCSS.Math.Content.K.CC.B.5
Count to answer ''how many?'' questions about as many as 20 things arranged in a line, a rectangular array, or a circle, or as many as 10 things in a scattered configuration; given a number from 1-20, count out that many objects.

-Kindergarten, Algebraic Thinking

• CCSS.Math.Content.K.OA.A.3
Decompose numbers less than or equal to 10 into pairs in more than one way, e.g., by using objects or drawings, and record each decomposition by a drawing or equation (e.g., 5 = 2 + 3 and 5 = 4 + 1).

-Kindergarten, Algebraic Thinking

• CCSS.Math.Content.K.OA.A.4
For any number from 1 to 9, find the number that makes 10 when added to the given number, e.g., by using objects or drawings, and record the answer with a drawing or equation.

-Kindergarten, Number & Operations

• CCSS.Math.Content.K.NBT.A.1
Compose and decompose numbers from 11 to 19 into ten ones and some further ones, e.g., by using objects or drawings, and record each composition or decomposition by a drawing or equation (such as 18 = 10 + 8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.