Lesson 4

Subtract with Mental Math

Est. Class Sessions: 2
X

Mathematical Standards

2.NBT.B
Use place value understanding and properties of operations to add and subtract. (2.NBT.B.6, 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

MP1.
Make sense of problems and persevere in solving them.
MP2.
Reason quantitatively.
MP3.
Construct viable arguments and critique the reasoning of others.
MP4.
Model with mathematics.
MP6.
Attend to precision.
MP8.
Look for and express regularity in repeated reasoning.

Students explore estimation of differences to one thousand. They develop strategies for solving multidigit subtraction problems and use estimation to check for reasonableness.

Content in this Lesson

  • Subtracting multidigit numbers using mental math strategies (e.g., composing and decomposing numbers, counting) with base-ten pieces and number lines [E6].
  • Estimating differences using mental math strategies (e.g., rounding using benchmarks, using friendly numbers, composing and decomposing numbers, counting) [E8].
  • Knowing what is important to solve a problem [MPE1].
  • Finding an efficient strategy for solving a problem [MPE2].
  • Using estimation to check for reasonableness [MPE3].
  • Showing or telling how to solve a problem [MPE5].
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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 Student Pairs

set of base-ten pieces (2 packs, 11 flats, 20 skinnies, 21 bits)

Materials for the Teacher

Display of Swimathon (Student Activity Book) Pages 741–742
Display of Mental Math Subtraction Strategies (Student Activity Book) Pages 743–744
Display of Open Number Lines Master (Teacher Guide)
Unit 14 Assessment Record
Shark Swimathon by Stuart J. Murphy
Estimation Strategies for Addition chart from Lesson 2
Display set of base-ten pieces (2 packs, 11 flats, 20 skinnies, 21 bits)
chart paper

Materials Preparation

Prepare Estimation Strategies Chart. Prepare a chart by writing "Estimation Strategies for Subtraction" on a large piece of chart paper.

Assessment in this Lesson

Assessment Expectation Assessed Math Practices Expectation Assessed
Use Mental Math to Subtract
with Feedback Box
Student Activity Book
Pages 745–746
E6. 
Add and subtract multidigit numbers using mental math strategies (e.g., composing and decomposing numbers, counting) with base-ten pieces and number lines.
E8. 
Estimate sums and differences using mental math strategies (e.g., rounding using benchmarks, using friendly numbers, composing and decomposing numbers, counting).
MPE1. 
Know the problem. I read the problem carefully. I know the questions to answer and what information is important.
MPE2. 
Find a strategy. I choose good tools and an efficient strategy for solving the problem.
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.