This 6 lesson unit focuses on the comparative mode of subtraction, and has students using connecting cubes to explore subtraction through five different models, counting, sets, number line, pan balance equations, and inverse of addition. Students will explore the relationship between addition and subtraction, use comparison in writing story problems, and practice subtraction facts and fact families. The lessons will build on and extend early understandings of counting, addition, and subtraction.

**Individual Lessons**

- Lesson 1: Counting Back and Counting On
- This lesson, which focuses on subtracting 1 from numbers to 10, begins with reading a counting book. The students model the numbers as the book is read. Then they make a chain of links and write in vertical and horizontal format the differences suggested by adding and subtracting one link at a time from their chains. Finally, they draw a chain showing one link being taken away and write in two formats the difference it represents.

- Lesson 2: Comparing Sets
- In this lesson students will be reviewing counting back by writing, estimating, and mentally computing whole number subtraction. They will count sets and record them in tables, which they will then use to draw conclusions. Students will also review the additive identity in the context of comparing sets.

- Lesson 3: Using the Number Line to Compare
- This lesson focuses on determining differences based on linear measurement, having students compare lengths using the number line. Students will then solve and create puzzles on number lines.

- Lesson 4: Balancing
- In this lesson students will explore subtraction through another model, the balance. The balance model leads naturally to recording equations. Students will write out in equation form the subtraction modeled on a pan balance, and then write out addition sentences that are from the same fact family.

- Lesson 5: Fact Families
- This lesson focuses on recording fact families, which students will use to explore the relationship between related addition and subtraction facts. Students will use connecting cubes and calculators to find missing addends, review the additive identity, and record fact families given either two addends or one addend and the sum.

- Lesson 6: Looking Back and Moving Forward
- This lesson reviews the work of the previous lessons, suggesting a framework for summative assessment. Students will use the knowledge and skills developed previously to demonstrate understanding while playing subtraction games.

**Subject(s): **Mathematics

**Grade Level(s): **K, 1

**Suggested Technology: **
Computer for Presenter, Computers for Students, Internet Connection, LCD Projector, Adobe Flash Player, Adobe Acrobat Reader, Java Plugin

**Instructional Time: **
6 Hour(s)

**Resource supports reading in content area:**Yes

**Freely Available: ** Yes

**Keywords: **subtraction, compare, number line, additive identity, difference, addend, story problem, number sentence, sum, addition,

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### Additional Information/Instructions

*By Author/Submitter*
References to counting books (pick two for lesson 1):

- Bang, Mollie.
*Ten, Nine, Eight*. New York: Greenwillow, 1983.
- Christelow, Eileen.
*Five Little Monkeys Jumping on the Bed*. New York: Scholastic, 1989.
- McGrath, Barbara Barbieri.
*The M&M's Counting Book*. New York: Scholastic, 1994.
- Morozumi, Atsuko.
*One Gorilla*. New York: Trumpet Club, 1990.
- Wise, William.
*Ten Sly Piranhas*. New York: Dial, 1993.

Reference to book for lesson 5:

- Williams, Rozanne Lanczak.
*Ten Monsters in Bed*. Huntington Beach, California: Creative Teaching Press, 1995.

### SOURCE AND ACCESS INFORMATION

**Contributed by: **
Susan Cornwell

**Name of Author/Source: **Illuminations National Council of Teachers of Math

**District/Organization of Contributor(s): **Florida State University

**Is this Resource freely Available? **Yes

**Access Privileges: **Public

* Please note that examples of resources are not intended as complete curriculum.