Lesson 3 | Adding and Subtracting Within 20 | 2nd Grade Mathematics

Objective

Use mental math to add and subtract within 10.

Student-Facing

I can use mental math to add and subtract within 10.

Common Core Standards

Core Standards

The core standards covered in this lesson

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.

Operations and Algebraic Thinking

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

The foundational standards covered in this lesson

1.OA.C.6

Operations and Algebraic Thinking

1.OA.C.6 — Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

Criteria for Success

The essential concepts students need to demonstrate or understand to achieve the lesson objective

Fluently add and subtract with numbers less than 10.
Relate addition and subtraction with missing addend contexts.
Make meaning of missing numbers in different parts of the equation.
Model with ten frames to make connections to mental math strategies.

Warm Up

5-10 minutes

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Tips for Teachers

Suggestions for teachers to help them teach this lesson

Students will use their facts within-10 knowledge to fluently add and subtract especially in more unique places.
Using ten frames will help students to visualize and begin to use some mental math strategies.
Even if some students don't need to rely on ten frames it is important to continue to make connections to ten frames and how it can be used as a tool to support facts within 10.
Students will need to pay attention to where the missing number is within the problem.

Lesson Materials

Optional: Tens Frame Template (1 per student) — These can be laminated or in page protectors to reuse
Optional: Linking cubes — if needed for individual student support
Optional: Number Bond Template — if needed for individual student support

Anchor Tasks

Tasks designed to teach criteria for success of the lesson, and guidance to help draw out student understanding

15-25 minutes

Problem 1

Solve for the missing number. Use a ten frame to model your answer.

a. 6 + _____ = 9

b. 8 = 3 + _____

c. 4 + _____ = 7

Purpose

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Problem 2

Solve for the missing numbers.

a. _____ - 3 = 6

b. 2 = _____ - 5

c. _____ - 1 = 7

d. 8 - _____ = 2

Purpose

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Problem Set

A set of suggested resources or problem types that teachers can turn into a problem set

15-20 minutes

Target Task

A task that represents the peak thinking of the lesson - mastery will indicate whether or not objective was achieved

5-10 minutes

Solve to find the missing numbers.

a. _____ - 4 = 5

b. 7 = _____ + 3

c. 2 + _____ = 8

d. _____ - 2 = 5

e. 8 = _____ + 4

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.

Adding and Subtracting Within 20

Objective

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Student-Facing

Common Core Standards

Core Standards

Operations and Algebraic Thinking

Foundational Standards

Operations and Algebraic Thinking

Criteria for Success

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Warm Up

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Tips for Teachers

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Lesson Materials

Anchor Tasks

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Problem 1

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Purpose

Problem 2

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Purpose

Problem Set

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Target Task

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Student Response

Additional Practice

Word Problems and Fluency Activities

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