Adding and Subtracting Within 20

Lesson 2

Math

Unit 1

2nd Grade

Lesson 2 of 15

Objective


Use related facts to add and subtract within 10.

Student-Facing

I can use related facts to add and subtract within 10.

Common Core Standards


Core Standards

  • 2.OA.B.2 — Fluently add and subtract within 20 using mental strategies. By end of Grade 2, know from memory all sums of two one-digit numbers. See standard 1.OA.6 for a list of mental strategies.

Foundational Standards

  • 1.OA.B.4

Criteria for Success


  1. Relate addition and subtraction equations.
  2. Write related addition and subtraction equations to represent relationships shown in number bonds and other visuals.
  3. Know and use fact pairs to 10.

Warm Up

5-10 minutes


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Tips for Teachers


  • The first lessons of the year aim to support students in their goal of adding and subtracting fluently to 20. This lesson builds upon first grade work with facts to ten so that they can extend to 20 after Lesson 4.
  • In this lesson we use facts to 10 as we relate addition and subtraction. This builds on work from first grade and will help students extend to mental math strategies in Lesson 3.

Lesson Materials

  • Tens Frame Template (1 per student) — These can be laminated or in page protectors to reuse
  • Linking cubes (2 different color towers of 10 per student) — Two-sided counters could also be used as an alternative
  • Optional: Number Bond Template

Anchor Tasks

15-25 minutes


Problem 1

Find the missing pair to 10 and write a related addition and subtraction equation. 

a.   3 and  _____

b.   8 and _____

c.   _____ and 6

Purpose

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Problem 2

For each equation fill in the blank and write one related addition and subtraction sentence.

a.   _____ + 9 = 10

b.   4 + _____ = 10

Purpose

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Problem Set

15-20 minutes


Target Task

5-10 minutes


Problem 1

A set of linking cubes is shown below. Which 2 equations can be used to describe this picture?

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Student Response

Problem 2

Write 1 addition equation and 1 subtraction equation that relate to the numbers 10, 7, and 3 as shown in the ten frame below. 

addition equation:        _____= _____+ _____

subtraction equation:   _____ - _____ = _____

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

Use mental math to add and subtract within 10.

Lesson 3
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Lesson Map

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

Topic A: Adding and Subtracting within 10 and Counting

Topic B: Strategies to Add and Subtract within 20

Topic C: Story Problems within 20

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