Curriculum  /  Math  /  2nd Grade  /  Unit 2: Adding and Subtracting Within 100  /  Lesson 7

Adding and Subtracting Within 100

Lesson 7

Math

Unit 2

2nd Grade

Lesson 7 of 21

Objective

Use properties of operations and other strategies to add within 100.

Student-Facing

I can make benchmark numbers to add.

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.

Foundational Standards

  • 1.NBT.C.4
  • 1.NBT.C.5
  • 1.NBT.C.6

Criteria for Success

  1. Understand that addends can be decomposed to make friendly numbers or multiples of ten to add. 
  2. Decompose addends to make friendly numbers and add remaining addend to find total.

Tips for Teachers

  • In this lesson, students re-compose addends in helpful ways in order to find the total. They will rely on their knowledge of numbers to ten as they compose friendly numbers.
  • This builds off of their work from Lesson 3 and extends their work to numbers beyond 50. Representations are more abstract using number bonds to show how addends are being broken up to make friendly numbers. For students who need additional support decomposing and recomposing numbers, linking cubes can be given as a tool as they work towards more abstract modeling. 
  • When students are decomposing numbers using number bonds, it is helpful to organize the space so that the number that is being added to the second addend is close to it. For example, in this response to the Target Task, notice how when 14 was decomposed into 11 and 3, the 3 is written next to the 37 to more easily see how they combine to make 40. 

Lesson Materials

  • Optional: Linking cubes (100 per student total, at least 2 colors to show groups of 10 in alternating colors)
  • Optional: Base ten blocks (9 tens and 18 ones per student or small group)

Warm Up

5-10 minutes

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Anchor Tasks

15-25 minutes

Problem 1

Use number bonds to make a friendly number to solve.

a.   76 + 15 =

b.   39 + 45 =

c.   27 + 55 =

Purpose

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Problem 2

Althea says solving 29 + 53 is simple because it’s the same as adding 30 + 52.  Explain Althea’s thinking.

Purpose

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Problem 3

Solve the equation in two ways. Use number bonds to show your thinking. 

54 + 37 = 

Purpose

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Problem Set

15-20 minutes

Target Task

5-10 minutes

Solve. Use number bonds to show your thinking. 

a.   14 + 37 =

b.   64 + 29 =

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

Relate the standard algorithm for addition to other methods to add and explain thinking.

Lesson 8
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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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