Lesson 1

Combining and Partitioning

Est. Class Sessions: 2–3
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Mathematical Standards

1.OA.A
Represent and solve problems involving addition and subtraction. (1.OA.A.1)
1.OA.B
Understand and apply properties of operations and the relationship between addition and subtraction. (1.OA.B.3)
1.OA.C
Add and subtract within 20. (1.OA.C.6)

Standards for Mathematical Practice

MP1.
Make sense of problems and persevere in solving them.
MP2.
Reason quantitatively.
MP3.
Construct viable arguments and critique the reasoning of others.
MP5.
Use appropriate tools strategically.
MP7.
Look for and make use of structure.

Students identify tools and strategies to combine and partition numbers for sums to 10. They sort addition facts by their sums to identify ways to partition or separate a number into two parts.

Content in this Lesson

  • Adding numbers with sums to ten using invented, counting, and reasoning strategies [E7].
  • Identifying partitions of numbers to ten [E1].
  • Using strategies that apply the turn-around property of addition [E4].
  • Representing addition using counters, number lines, and ten frames [E2].
  • Representing partitions of numbers using box diagrams [E1].
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Materials for Students

Daily Practice and Problems Lesson Homework Assessment

Student Books

 Student Activity Book

Teacher Resources

 Teacher Guide - digital

Supplies for Students

20 connecting cubes or counters
desk number line (0–40)
chart paper, optional

Materials for the Teacher

Display of Sorting Mat Master (Teacher Guide)
Display of Box Diagram Master (Teacher Guide)
Display of Partitions of Five Master (Teacher Guide)
Display of Partitioning Six into Parts (Student Activity Book) Pages 119–120
Unit 6 Assessment Record
chart paper
5 connecting cubes
tape

Materials Preparation

Prepare Addition Cards. Copy and cut out one set of addition cards for each student pair using the Addition Cards for Small Sums 1–3 Masters. If possible, use heavy weight paper or card stock to make the cards. Bind or clip each set together.

Prepare Sorting Mats. For display, use the Sorting Mat Master to draw a Sorting Mat on chart paper. See Figure 1. Each student pair will also need a sorting mat. Use the Sorting Mat Master to make a sorting mat on 11–inch x 17–inch paper. To copy the mat from an 8.5 x 11–inch paper to 11 x 17–inch paper, increase the copy ratio to 130%. Sorting mats can also be drawn on chart paper. If students do not attach the addition cards, these mats can be used again in Lesson 8.

Figure 1: A sorting mat on chart paper

Prepare Addition Strategies Chart. Create a chart for recording addition strategies. Title the chart "Addition Strategies."

Assessment in this Lesson

Assessment Expectation Assessed
Partitioning Six into Parts
Check-In: Questions 5–6
Student Activity Book
Page 120
E7.
Add and subtract within 10 using invented, counting (e.g., counting on, counting up, counting back), and reasoning (e.g., making ten, using ten, doubles) strategies.