Lesson 2

Subtraction Seminar

Est. Class Sessions: 2–3
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Mathematical Standards

2.NBT.A
Understand place value. (2.NBT.A.1)
2.NBT.B
Use place value understanding and properties of operations to add and subtract. (2.NBT.B.6, 2.NBT.B.7, 2.NBT.B.8, 2.NBT.B.9)
2.MD.B
Relate addition and subtraction to length. (2.MD.B.6)
2.OA.A
Represent and solve problems involving addition and subtraction. (2.OA.A.1)

Standards for Mathematical Practice

MP2.
Reason quantitatively.
MP3.
Construct viable arguments and critique the reasoning of others.

Students develop strategies for solving subtraction problems with two- and three-digit numbers. Students share strategies, record them on a chart, and practice using the strategies to solve problems.

Content in this Lesson

  • Representing subtraction problems using base-ten pieces and number
    lines [E2].
  • Subtracting multidigit numbers using mental math strategies (e.g., composing and decomposing numbers, counting up) with number lines, 200 Charts, and base-ten pieces [E3].
  • Checking a solution for reasonableness [MPE3].
  • Showing or telling how to solve problems [MPE5].
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Materials for Students

Daily Practice and Problems Lesson Homework Assessment

Student Book

 Student Activity Book

Teacher Resources

 Teacher Guide - digital

Supplies for Student Pairs

base-ten pieces (21 bits, 20 skinnies, 5 flats)
100 connecting cubes
desk number line (0–100)

Materials for the Teacher

Display of Thinking about Subtraction Master (Teacher Guide)
Display of 200 Chart (Student Activity Book) Reference
Unit 9 Assessment Record
100 connecting cubes
Display set of base-ten pieces (21 bits, 20 skinnies, 5 flats)
chart paper
class number line (0–130) or prepared Number Line Display Masters from Unit 7

Materials Preparation

Prepare Subtraction Strategies Chart. Label a piece of chart paper “Subtraction Strategies Chart”. Display it and have several other sheets of chart paper on hand.

Assessment in this Lesson

Assessment Expectation Assessed Math Practices Expectation Assessed
Check Subtraction Problems
with Feedback Box
Student Activity Book
Pages 447–448
E2. 
Represent subtraction problems using base-ten pieces and number lines.
E3. 
Subtract multidigit numbers using mental math strategies (e.g., composing and decomposing numbers, counting up) with number lines,
a 200 Chart, and base-ten pieces.
MPE3. 
Check for reasonableness. I look back at my solution to see if my answer makes sense. If it does not, I try again.
MPE5. 
Show my work. I show or tell how I arrived at my answer so someone else can understand my thinking.

Vocabulary in this Lesson