Curriculum  /  Math  /  2nd Grade  /  Unit 2: Adding and Subtracting Within 100  /  Lesson 19

Adding and Subtracting Within 100

Lesson 19

Math

Unit 2

2nd Grade

Lesson 19 of 21

Objective

Use strategies to add and subtract within 100 and explain thinking.

Student-Facing

I can use strategies to add and subtract within 100 and explain my thinking. 

Common Core Standards

Core Standards

  • 2.NBT.B.5 — Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
  • 2.NBT.B.9 — Explain why addition and subtraction strategies work, using place value and the properties of operations. Explanations may be supported by drawings or objects.

Foundational Standards

  • 1.NBT.C.4
  • 1.NBT.C.5
  • 1.NBT.C.6
  • 1.OA.B.3
  • 1.OA.B.4

Criteria for Success

  1. Select a strategy to use to solve.
  2. Explain how to solve using a selected strategy. 

Tips for Teachers

  • This is a culminating lesson of students adding and subtracting within 100 using various strategies. While students will continue to work on this throughout their 2nd grade year, this lesson allows for students to flexibly use strategies they have worked with throughout this unit. 
  • For the Problem Set, a die is needed for students to complete one of the problems. If you don't have a die for every student, small groups or pairs can share. 
  • When looking at student explanations, keep an eye out for:
    • a description of the mathematical actions taken (adding, subtracting, decomposing or composing addends, rebundling units, etc.) and in what order.
    • explicit use the numbers that were used in the problem and their corresponding place values.

Lesson Materials

  • Dice (one per student or small group) — needed for Problem Set only

Warm Up

5-10 minutes

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Anchor Tasks

15-25 minutes

Problem 1

Solve your own way. Check your answer by solving a different way. 

a.   45 + 39 =

Solve: Check:

b.   88 - 26 =

Solve: Check:

Purpose

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Problem 2

Solve and explain your strategy. 

a.   79 - 37 = 

Solve: Check:

b.   29 + 61 =

Solve: Check:

c.   52 - 14 =

Solve: Check:

d.   100 - 46 =

Solve: Check:

Purpose

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Problem Set

15-20 minutes

Target Task

5-10 minutes

Solve and explain your thinking.

a.   93 - 27 = ____

b.   45 + 46 = ____

Student Response

Additional Practice

Daily Word Problems, Warm Ups, and Center Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Word Problems and Fluency Activities

Next

Interpret and create picture graphs and answer related questions.

Lesson 20
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Adding & Subtracting with Multiples of Ten

Topic B: Strategies for Adding within 100

Topic C: Strategies for Subtracting within 100

Topic D: Working within 100 and Categorical Data

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