Lesson 8 | Rounding, Addition, and Subtraction | 3rd Grade Mathematics

Objective

Add numbers with up to one composition within 1,000.

Common Core Standards

Core Standards

The core standards covered in this lesson

3.NBT.A.2 — Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

Number and Operations in Base Ten

3.NBT.A.2 — Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

Foundational Standards

The foundational standards covered in this lesson

2.NBT.B.5

Number and Operations in Base Ten

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.7

Number and Operations in Base Ten

2.NBT.B.7 — Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

Criteria for Success

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

Add three-digit numbers with one composition.
Understand an algorithm to be a "set of predefined steps…that gives the correct result in every case when the steps are carried out correctly" (NBT Progression, p. 3).
Solve one-step word problems involving three-digit addition with one composition.

Tips for Teachers

Suggestions for teachers to help them teach this lesson

When discussing how to line up numbers in order to add or subtract them vertically, emphasize that units need to be lined up because one can only add or subtract like units (ones with ones and tens with tens), as opposed to saying that numbers need to be lined up from right to left. This is an important distinction since lining numbers up from right to left no longer works when students begin working with decimals (e.g., adding 6.4 and 2.08 would result in an incorrect sum if lined up from right to left).
Students have solved one-step word problems involving addition in previous grade levels (1.OA.1, 2.OA.1), just not yet with whole numbers of this magnitude. So, the intention of the word problems in this lesson is to have students solve contextual problems that involve computations expected of this grade level (3.NBT.2) as well as prepare students to solve two-step word problems involving addition and subtraction later in the unit, and eventually all four operations in Units 2 and 3 (3.OA.8).

Lesson Materials

Thousands place value chart (1 per student) — Students might need more or less depending on their reliance on this tool.
Optional: Base ten blocks (5 hundreds, 7 tens, and 14 ones per student or pair of students) — Students might not need these depending on their reliance on concrete materials. Students could also use Paper base ten blocks instead. See Anchor Task 1 Notes for more information.

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Anchor Tasks

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

Problem 1

Mr. Silver and Mrs. Ingall want to know the largest number they can represent with their base ten blocks.

Mr. Silver has 4 tens, 2 hundreds, and 6 ones. Mrs. Ingall has 2 tens, 3 hundreds, and 8 ones. What’s the largest number they could represent with their base ten blocks? Show or explain how you know.

Guiding Questions

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Problem 2

a. Rosa and Zayn showed how they found the value of $$265+493$$. Explain how each method works.

Rosa's work:	Zayn's work:

b. Solve using Rosa or Zayn’s method. Show or explain your work.

$$82+56=$$ _______

_______ = $$328+149$$

$$40+792=$$ _______

Guiding Questions

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Problem 3

I received an awesome new book from the library recently. I read 443 pages the first week and 237 pages the second week. How many pages did I read in total?

Guiding Questions

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Problem Set

Problem Set

Answer Keys

Unlock the answer keys for this lesson's problem set and extra practice problems to save time and support student learning.

Discussion of Problem Set

Why is it important to align numbers by place value when using the standard algorithm?
What was similar about #1a-c? What was different?
Look at #3. Whose calculation was correct? How might the other student have gotten their incorrect answer?
Did you use any mental strategies? For which problems? Why?

Target Task

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

Problem 1

Solve. Show or explain your work.

a. 57 + 423 = ______

b. __________ = 81 + 65

c. 635

+ 248

Student Response

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Problem 2

There are 382 leaves on the yellow tree and 580 leaves on the green tree. What is the total number of leaves on both trees?

Student Response

An example response to the Target Task at the level of detail expected of the students.

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Additional Practice

The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency 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.

Extra Practice Problems

Extra Practice Problems

Answer Keys

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Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Lesson 7

Lesson 9

Lesson Map

Topic A: Foundations of Place Value

Use counting, place value understanding, and addition/subtraction of ones and tens to complete a partially filled-in number grid.

3.NBT.A.1 3.NBT.A.2

Represent three-digit numbers using concrete manipulatives and drawings, including cases with more than 9 of any unit.

3.NBT.A.1 3.NBT.A.2

Locate three-digit numbers on a number line and explain their placement.

3.NBT.A.1

Topic B: Rounding to the Nearest Ten and Hundred

Define estimation and its purpose. Round two-digit numbers to the nearest ten using a number line.

3.NBT.A.1

Round three-digit numbers to the nearest hundred using a number line.

3.NBT.A.1

Round three-digit numbers to the nearest ten using a number line.

3.NBT.A.1

Round multi-digit numbers to any place in more complex cases, including those involving real-world contexts and/or assessing the reasonableness of that estimate.

3.NBT.A.1

Topic C: Addition and Subtraction Within 1,000

Add numbers with up to one composition within 1,000.

3.NBT.A.2

Add numbers with multiple compositions within 1,000.

3.NBT.A.2

Solve one-step word problems involving addition, using rounding to assess the reasonableness of answers.

3.NBT.A.1 3.NBT.A.2 3.OA.D.8

Subtract numbers with up to one decomposition within 1,000.

3.NBT.A.2

Subtract numbers with multiple decompositions within 1,000.

3.NBT.A.2

Solve one-step word problems involving subtraction, using rounding to assess the reasonableness of answers.

3.NBT.A.1 3.NBT.A.2 3.OA.D.8

Solve one- and two-step word problems involving addition and subtraction, using rounding to assess the reasonableness of answers.

3.NBT.A.1 3.NBT.A.2 3.OA.D.8

Rounding, Addition, and Subtraction

Objective

Common Core Standards

Core Standards

Number and Operations in Base Ten

Foundational Standards

Number and Operations in Base Ten

Number and Operations in Base Ten

Criteria for Success

Tips for Teachers

Lesson Materials

Anchor Tasks

Problem 1

Guiding Questions

Problem 2

Guiding Questions

Problem 3

Guiding Questions

Problem Set

Discussion of Problem Set

Target Task

Problem 1

Student Response

Problem 2

Student Response

Additional Practice

Extra Practice Problems

Word Problems and Fluency Activities

Lesson Map

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