Curriculum  /  Math  /  3rd Grade  /  Unit 1: Rounding, Addition, and Subtraction  /  Lesson 8

Rounding, Addition, and Subtraction

Lesson 8

Math

Unit 1

3rd Grade

Lesson 8 of 14

Objective

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

Common Core Standards

Core Standards

  • 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

  • 2.NBT.B.5
  • 2.NBT.B.7

Criteria for Success

  1. Add three-digit numbers with one composition.
  2. 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).
  3. Solve one-step word problems involving three-digit addition with one composition.

Tips for Teachers

  • 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

25-30 minutes

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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Student Response

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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. 

  1. $$82+56=$$ _______

  1.  _______ = $$328+149$$
  1. $$40+792=$$ _______

Guiding Questions

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Student Response

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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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Student Response

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Problem Set

15-20 minutes

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

5-10 minutes

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

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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.

Word Problems and Fluency Activities

Word Problems and Fluency Activities

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

Next

Add numbers with multiple compositions within 1,000.

Lesson 9
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Lesson Map

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Topic A: Foundations of Place Value

Topic B: Rounding to the Nearest Ten and Hundred

Topic C: Addition and Subtraction Within 1,000

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