Adding and Subtracting Within 1,000

Lesson 1

Math

Unit 5

2nd Grade

Lesson 1 of 25

Objective


Mentally add 10 and 100 to numbers within 1,000.

Student-Facing

I can mentally add 10 and 100 to numbers within 1,000.

Common Core Standards


Core Standards

  • 2.NBT.B.8 — Mentally add 10 or 100 to a given number 100—900, and mentally subtract 10 or 100 from a given number 100—900.

Foundational Standards

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

Criteria for Success


  1. Count on by 10 or 100 to find the total. 
  2. Know that when you add a ten the value of the tens place will increase or in some cases a change in the hundreds place when the count crosses the next hundred. 
  3. Know that when you add a hundred the value of the hundreds place will increase.

Warm Up

5-10 minutes


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Tips for Teachers


Students will need to fluently add 10 or 100 to three-digit numbers to 1,000 which requires that students have a firm grasp of the count sequence to 1,000. Using completed hundreds charts to 1,000 from Unit 4 may be a helpful resource for students to make a connection between three-digit numbers and adding a ten or a hundred. 

Lesson Materials

  • Optional: Blank Hundreds Chart (1 per group) — Students can create a hundreds chart to 1,000 for reference
  • Base ten blocks (10 hundreds, 18 tens, 18 ones per student)

Anchor Tasks

15-25 minutes


Problem 1

Some of the numbers from the hundreds chart are missing. Find the missing numbers based on what we know. 

a.    

123 124
133  
143  

b.    

150
 
170
 

c.    

189
 
 
219

d.    

192
 
 

Purpose

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Problem 2

Build the number 184 with base ten blocks.

a.   What number is made if we add 100?

b.   What number is made if we add another 100 to the new number that was made?

c.   In parts a and b, what digit changes? What digit(s) stay the same?

d.   Solve the following and think about what digits stay the same and which change.

  1. 273 + 100 = _____
  2. 100 + 500 =_____
  3. 100 + 847 = _____

Purpose

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Problem 3

Each jump between each tick mark on the number line counts by the same value. Find the missing number in each number line. Write the equation you used to find the missing number.

a.   _____ + _____ = _____

b.   _____ + _____ = _____

c.   _____ + _____ = _____

d.   _____ + _____ = _____

e.   _____ + _____ = _____

Purpose

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Problem Set

15-20 minutes


Target Task

5-10 minutes


Use mental math to find the missing numbers.

a.   10 + 545 = _____

b.   190 + 10 = _____

c.   125 + 100 = _____

d.   680 + 100 = _____ 

e.   370 + 10 = _____

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

Add multiples of 10 and 100 to numbers within 1,000.

Lesson 2
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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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