THIRD GRADE UNIT 1 Numbers and Operations in Base Ten
3 Weeks
In this unit students will:
 Demonstrate place value understanding beyond algorithms or procedure for rounding.
 Round numbers to the nearest 10s and 100s
 Estimate sum and/or difference of numbers
 Apply estimation to solve problems, and determine when it is necessary or appropriate to apply estimation strategies
 Add and subtract numbers within 1000 fluently, accurately, efficiently (using a reasonable amount of steps and time), and flexibly using a
variety of strategies BEYOND the standard algorithm
 Add and subtract both vertically and horizontally and apply the commutative and associative properties.
 Understand how to use an inverse operation to verify computation accuracy.
Unit 1 Overview Video
Vocabulary Cards
Parent Letter
Parent Guides
Prerequisite Skills Assessment
Number Talks Calendar
(all documents in the outline file)
Topic 1: Addition & Subtraction Strategies
Big Ideas/Enduring Understandings:
 As students continue to add and subtract within 1000, they achieve fluency with strategies and algorithms that are based on place value,
properties of operations, and/or the relationship between addition and subtraction.
 When rounding to the nearest 10, the goal is to approximate the number by the closest number that has no ones. When rounding to the
nearest 100, the goal is to approximate the number by the closest number that has no tens and no ones. Place Value and Rounding…
 Addition and subtraction are inverse operations; one undoes the other.
Essential Questions:
 How can I use different strategies to help me fluently add and subtract?
 How can the place value system help me to round whole numbers?
Content Standards
Content standards are interwoven and should be addressed throughout the year in as many different units and activities as possible in order to
emphasize the natural connections that exist among mathematical topics.
Use place value understanding and the properties of operations to perform multi-digit arithmetic. (A range of algorithms may be used.)
MGSE3.NBT.1 Use place value understanding to round whole numbers to the nearest 10 or 100.
MGSE3.NBT.2 Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the
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relationship between addition and subtraction.
Vertical Articulation of Addition and Subtraction Using Place Value
First Grade Operations with Place Value
Second Grade Operations with Place Value
Fourth Grade Operations with Place Value
Standards
Standards
Standards
MGSE1.NBT.2 Understand that the two digits of a MGSE2.NBT.1 Understand that the three digits of MGSE4. NBT.1 Recognize that in a multitwo-digit number represent amounts of tens and
a three-digit number represent amounts of
digit whole number, a digit in one place
ones.
hundreds, tens, and ones
represents ten times what it represents in
MGSE1.NBT.4 Add within 100, including adding a
MCC2NBT.3 Read and write numbers to 1000
the place to its right.
two-digit number and a one-digit number, and
using base-ten numerals, number names, and
MGSE4.NBT.2 Read and write multi-digit
adding a two-digit number and a multiple of 10,
expanded form.
whole numbers using base-ten numerals,
using concrete models or drawings and strategies MCC2NBT.4 Compare two three-digit numbers
number names, and expanded form.
based on place value, properties of operations,
based on meanings of the hundreds, tens, and
Compare two multi-digit numbers based on
and/or the relationship between addition and
ones digits, using >, =, and < symbols to record
meanings of the digits in each place, using
subtraction; one adds tens and tens, ones and
the results of comparisons.
>, =, and < symbols to record the results of
ones; and sometimes it is necessary to compose a 8 See
comparisons.
ten.
MCC2NBT.5 Fluently add and subtract within 100 MGSE4.NBT.3 Use place value
MGSE1.NBT.5 Given a two-digit number, mentally using strategies based on place value, properties
understanding to round multi-digit whole
find 10 more or 10 less than the number, without of operations, and/or the relationship between
numbers to any place.
having to count; explain the reasoning used.
addition and subtraction.
MGSE4.NBT.4 Fluently add and subtract
MCC2NBT.6 Add up to four two-digit numbers
multi-digit whole numbers using the
using strategies based on place value and
standard algorithm.
properties of operations.
MCC2NBT.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.
MCC2.NBT.9 Explain why addition and
subtraction strategies work, using place value and
the properties of operations.
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Place Value Instructional Strategies
Prior to implementing rules for rounding, students need to have opportunities to investigate place value. A strong understanding of place value is
essential for the developed number sense and the subsequent work that involves rounding numbers.
Dependence on learning rules or mnemonics can be eliminated with strategies such as the use of a number line to determine which multiple of 10 or
of 100 a number is closer. (5 or more rounds up, less than 5 rounds down). As students’ understanding of place value increases, the strategies for
rounding are valuable for estimating, justifying, and predicting the reasonableness of solutions in problem-solving.
Continue to use manipulatives such as hundreds charts and place-value charts. Have students use a number line or a roller coaster example to block
off the numbers in different colors.
For example, this chart shows which numbers will round to the tens place.
Strategies used to add and subtract two-digit numbers are now applied to fluently add and subtract whole numbers within 1000. These strategies
should be discussed so that students can make comparisons and move toward efficient methods.
Number sense and computational understanding is built on a firm understanding of place value.
This standard refers to fluently, which means accuracy, efficiency (using a reasonable amount of steps and time), and flexibility (using
strategies such as the distributive property). The word algorithm refers to a procedure or a series of steps. There are other algorithms other
than the standard algorithm. Third grade students should have experiences beyond the standard algorithm. A variety of algorithms will be
assessed.
Problems should include both vertical and horizontal forms, including opportunities for students to apply the commutative and associative
properties. Students explain their thinking and show their work by using strategies and algorithms, and verify that their answer is reasonable.
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236 – 79 =
326 + 247 =
(326 – 3) + (247 + 3) =
323 + 250 = 573
This example shows how a
student could use
compensation to solve an
addition problem.
1 + 20 + 100 + 36 = 157
This third grader used an open number line
by adding up in chunks. He started at 79
and counting up to 236 in order to
subtract.
Students are encouraged to use this strategy
in a way that makes sense to them.
178 + 225 = ?
178 + 200 = 378
378 + 20 = 398
This third grader used an open number line by adding first the hundreds, then the tens and finally the
ones.
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Place Value Common Misconceptions
The use of terms like “round up” and “round down” confuses many students. For example, the number 37 would round to 40 or they say it “rounds
up”. The digit in the tens place is changed from 3 to 4 (rounds up). This misconception is what causes the problem when applied to rounding down.
The number 32 should be rounded (down) to 30, but using the logic mentioned for rounding up, some students may look at the digit in the tens place
and take it to the previous number, resulting in the incorrect value of 20. To remedy this misconception, students need to use a number line to
visualize the placement of the number and/or ask questions such as: “What tens are 32 between and which one is it closer to?” Developing the
understanding of what the answer choices are before rounding can alleviate much of the misconception and confusion related to rounding.
Evidence of Learning
Place Value and Rounding
 Demonstrate place value understanding beyond algorithms or procedure for rounding.
 Round numbers to the nearest 10s and 100s
 Estimate sum and/or difference of numbers
 Apply estimation to solve problems, and determine when it is necessary or appropriate to apply estimation strategies
 Explain and reason about the answers which are the result of rounding.
 Utilize a number line and a hundreds chart as tools to support their work with rounding.
Addition and Subtraction
 Fluently add and subtract numbers within 1000 , accurately, efficiently (using a reasonable amount of steps and time), and flexibly using a
variety of strategies BEYOND the standard algorithm
 Add and subtract both vertically and horizontally and apply the commutative and associative properties.
 Understand how to use an inverse operation to verify computation accuracy.
Assessments:
Prerequisite Skills: Pre-assessment test
 Students understand the base-ten system. Students worked with counting in fives, tens and multiples of hundreds, tens and ones. Students
also recognize that the digits in each place of a number represent the amounts of thousands, hundreds, tens, or ones. A strong understanding
of place value is essential for the developed number sense and the subsequent work that involves rounding numbers.
 Students use their understanding of addition to develop fluency within 100. They solve problems within 1,000 by using models of addition and
subtraction
 Students should have numerous experiences using a number line and a hundreds chart as tools to support their work with rounding.
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Additional Assessments:
 Formative Assessment Lessons
ELEMENTARY FORMATIVE ASSESSMENT LESSONS
Adopted Resources
My Math:
Reminder: The Standard Algorithms for addition and
subtraction are taught in grade 4
Chapter 1: Place Value
1.1 Thousands
1.2 Compare Numbers
1.3 Order Numbers
1.4 Round to Nearest Ten
1.5 Round to Nearest Hundred
1.6 Problem Solving
Chapter 2: Addition
2.1 Addition Properties
2.4 Add Mentally
2.5 Estimate Sums
2.6 Adding 3 Numbers
2.9 Problem Solving
Chapter 3: Subtraction
3.1 Subtract Mentally
3.2 Estimate Differences
3.3 Problem Solving
3.4 Subtraction
Adopted Online Resources
My Math
http://connected.mcgrawhill.com/connected/login.do
Teacher User ID: ccsde0(enumber)
Password: cobbmath1
Student User ID: ccsd(student ID)
Password: cobbmath1
Examplar
http://www.exemplarslibrary.com/
User: Cobb Email
Password: First Name

What’s the Problem?
First in Math
http://www.firstinmath.com
Student User ID:
Password:
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Strategies for Subtraction MGSE3.NBT.2
Think Math
Chapter 1: Building Operations
1.1 Counting and Larger Numbers
1.2. Making 10, Adding 10
1.4 Counting on a Number Line
1.5 Adding on a Number Line
1.6 Subtracting on the Number Line
1.8 Finding Missing Parts
Chapter 3: Using Addition and Subtraction
3.1 Magic Square
3.2 Magic Squares
Chapter 5: Understanding Addition and
Subtraction
5.1 Grouping by Tens
5.2 Rounding to the Nearest Ten or Hundred
5.3 Finding Differences
5.4 Using Tens and Hundreds to Estimate
5.5 Estimate and to Find the Sum
Chapter 14: Addition and Subtraction in Depth
14.1 Place Value
14.2 Breaking Up Numbers to Add
14.3 Breaking Up Numbers to Subtract
14.4 Comparing Addition and Subtraction
14.5 Addition Shortcuts and Rounding
14.6 Addition and Subtraction Situations
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Additional Web Resources:
National Council of Teachers of Mathematics, Illuminations:
K-5 Math teaching Resources
Mathematics TEKS Toolkit
http://illuminations.nctm.org/Lesson.aspx?id=754
http://www.k-5mathteachingresources.com/3rd-grade-number-activities.html
http://www.utdanacenter.org/mathtoolkit/instruction/lessons/3_hundred.php
Estimation 180 is a website of 180 days of estimation ideas that build number sense. http://www.estimation180.com/days.html
Illustrative Mathematics provides instructional and assessment tasks, lesson plans, and other resources. https://www.illustrativemathematics.org/
http://www.insidemathematics.org
http://www.yummymath.com
http://www.gregtang.com
Suggested Manipulatives
base ten blocks
place value chart
open number line
hundred chart
Task Descriptions
Scaffolding Task
Constructing Task
Practice Task
Culminating Task
3rd Grade Unit 1
Vocabulary
place value
equation
addend
sum
difference
Suggested Literature
Lights Out
How Much, How Many, How Far, How Heavy, How
Long, How Tall is 1000?
Shark Swimathon
Safari Park
Mall Mania
The Warlord’s Beads
The King’s Commissioners
Coyotes All Around
Task that build up to the learning task.
Task in which students are constructing understanding through deep/rich contextualized problem solving
Task that provide students opportunities to practice skills and concepts.
Task designed to require students to use several concepts learned during the unit to answer a new or unique situation.
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Formative Assessment
Lesson (FAL)
3-Act Task
Lessons that support teachers in formative assessment which both reveal and develop students’ understanding of key
mathematical ideas and applications.
Whole-group mathematical task consisting of 3 distinct parts: an engaging and perplexing Act One, an information and
solution seeking Act Two, and a solution discussion and solution revealing Act Three.
Unit 1 Tasks - Addition and Subtraction Using Place Value
Task Name
Task Type
Grouping Strategy
Scaffolding Tasks
Three Other Ways
Island Hop
Shake, Rattle, and Roll
The Great Round Up!
Mental Mathematics
Perfect 500!
Take 1,000
3rd Grade Unit 1
Partners/Small Group
Task
Constructing Task
Whole/Small Group Task
Constructing Task
Partner/Small Group Task
Practice Task
Small Group Task
Constructing Task
Whole Class Task
Constructing Task
Small Group/Partner Task
Constructing Task
Partner/Small Group Task
Description
Content Addressed
Standard(s)
Place Value, Addition
and Subtraction
Rounding numbers to the
nearest 10
Rounding, Using
estimation and mental
math with addition
Place Value, Rounding
Using and sharing mental
math strategies
Mental Math with sums
of 100
Mental Math with
combinations of 100
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MGSE3.NBT.1
MGSE3.NBT.2
This task provides an opportunity for students to
decompose numbers in multiple ways. This will help
them easily manipulate numbers as needed in
computation, as well as understand the value of digits in
numbers when rounding.
This task is an introductory lesson for
MGSE3.NBT.1 rounding. Students build this understanding
using a number line.
This task focuses on rounding as well as the
MGSE3.NBT.1
understanding of the value of a digit.
MGSE3.NBT.2
This task is used to help develop the
MGSE3.NBT.1 understanding of the value of a digit as well as
to support rounding concepts.
This task builds on the idea of various mental
MGSE3.NBT.2 math strategies that could easily be addressed in
Number Talks throughout the year.
This task involves estimation with addition. It
MGSE3.NBT.2 utilizes many mental math strategies developed
in number talks and prior tasks.
This task involves estimation with addition. It
MGSE3.NBT.2 utilizes many mental math strategies developed
in Number Talks and prior tasks.
2015-2016
Piggy Bank
Let’s Think About
Addition and
Subtraction!
The Power of
Properties
Take Down!
Happy to Eat Healthy
Field Day Fun
I Have a Story, You
Have a Story
Culminating Task:
What’s the Story
Here?
3rd Grade Unit 1
3-Act Task
Whole Group
Addition/Subtraction
Problem Solving
MGSE3.NBT.2
Scaffolding Tasks
Individually, Pairs, or
Small Group Task
Constructing Task
Individual/Partner Task
Practice Task
Partner Task
Constructing Task
Individual/Partner Task
Constructing Task
Individual/Partner Task
Constructing Task
Individual/Partner Task
Performance Task
Individual/Partner Task
Addition, Subtraction
Commutative, Identity
and Associative
Properties
Subtraction
In this task, students will view a video and tell what they
noticed. Next, they will be asked to discuss what they
wonder about or are curious about. Students will then
use mathematics to answer their own questions.
In this task, students will solve word problems
MGSE3.NBT.2 requiring addition and subtraction.
This task builds on the relationship of addition
MGSE3.NBT.2 and subtraction by developing
the understanding of the properties.
In this task, students will use mental math to
MGSE3.NBT.2 solve subtraction problems.
In this task, students use a menu to decide
MGSE3.NBT.1
which items to purchase given a specific
MGSE3.NBT.2
amount of money to spend
In this task, students will solve addition and
MGSE3.NBT.2 subtraction word problems.
Addition/Subtraction
Problem Solving
Addition/Subtraction
Problem Solving
Understanding and
writing addition and
subtraction word
problems
MGSE3.NBT.2
Addition, Subtraction,
Rounding
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In this task, students will write their own story
problems.
In this task, students will create a book based on
all standards covered in Unit 1. This
MGSE3.NBT.1 culminating task represents the level of depth,
MGSE3.NBT.2 rigor, and complexity expected of all third
grade students to demonstrate evidence of
learning.
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