Curriculum  /  Math  /  2nd Grade  /  Unit 5: Adding and Subtracting Within 1,000  /  Lesson 13

Adding and Subtracting Within 1,000

Lesson 13

Math

Unit 5

2nd Grade

Lesson 13 of 25

Objective

Use constant difference to subtract by subtracting multiples of ten or a hundred.

Student-Facing

I can make a friendly number to subtract multiples of ten or hundred. 

Common Core Standards

Core Standards

  • 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.

Foundational Standards

  • 1.NBT.B.2
  • 2.NBT.A.1
  • 2.NBT.A.2

Criteria for Success

  1. Recognize how and compose a multiple of 10 or 100 with the subtrahend by adding. 
  2. Add the same amount to the minuend to keep the difference in the problem and convert to an easier problem. 
  3. Use a mental strategy to complete the subtraction by subtracting a multiple of 10 or 100. 

Tips for Teachers

Using tape diagrams to represent the minuend and subtrahend can be a helpful way for students to visualize why constant-difference works as a subtraction strategy. Students see that when the same amount is added to both numbers, the difference is preserved. Unit 2 Lesson 12 explores the idea of constant difference within 100 if students need a refresher before applying to computations within 1,000. 

Warm Up

5-10 minutes

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Anchor Tasks

15-25 minutes

Problem 1

a.   How much more to the next multiple of 10? What is it?

  1. 48 
  2. 77 
  3. 95

b.   How much more to the next multiple of 100? What is it?

  1. 98 
  2. 190 
  3. 394 

Purpose

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Problem 2

Karla solved 310 - 99 = ? by making a friendly number to subtract. 

a.   What do you notice about Karla's strategy?

b.   Use Karla's strategy and make the next multiple of ten or a hundred to subtract. 

  1. 400 - 97 = _____
  2. 525 - 295 = _____
  3. 400 - 198 = _____
  4. 446 - 39 = _____

Purpose

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Problem 3

Make a friendly number to solve. 

a.   389 - 57 = _____

b.   771 - 98 = _____

Purpose

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Problem Set

15-20 minutes

Target Task

5-10 minutes

Make a friendly number to subtract. 

a.   600 - 190 = _____

b.   510 - 97 = _____

c.   450 - 298 = _____

d.   493 - 65 = _____

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 concrete manipulatives to subtract within 1,000 with no decompositions.

Lesson 14
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Lesson Map

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

Topic A: Adding with Mental Strategies

Topic B: Adding within 1,000

Topic C: Subtracting with Mental Strategies

Topic D: Subtracting within 1,000

Topic E: Story Problems and Explaining Addition and Subtracting Thinking

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