Students estimate quantities using rounding and develop fluency with the standard algorithm of addition and subtraction. Students focus on the precision of their calculations, and use them to solve realworld problems.
Math
Unit 1
3rd Grade
In the first unit of 3rd grade, students will build on their understanding of the structure of the place value system from 2nd grade (MP.7) to estimate values by rounding them (3.NBT.1) and develop fluency with the standard algorithm of addition and subtraction (3.NBT.2). Throughout the unit, students attend to the precision of their calculations (MP.6) and use them to solve realworld problems (MP.4).
In 2nd grade, students developed an understanding of the structure of the baseten system as based in repeated bundling in groups of 10. With this deepened understanding of the place value system, students "add and subtract within 1000, with composing and decomposing, and they understand and explain the reasoning of the processes they use" (NBT Progressions, p. 8). These processes and strategies include concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction (2.NBT.7). As such, at the end of 2nd grade, students are able to add and subtract within 1,000 using a variety of strategies including algorithms, but are not yet fluent with them.
Because all students are not yet fluent with place value strategies, Unit 1 starts off by reinforcing some of the place value understanding that students learned in 2nd grade. Students use this sense of magnitude and the idea of benchmark numbers to first place numbers on number lines of various endpoints and intervals, and next use those number lines as a model to help them round twodigit numbers to the tens place as well as threedigit numbers to the hundreds and tens place (3.NBT.1). Next, students focus on developing their fluency with the addition and subtraction algorithms up to 1,000, making connections to the place value understandings and other models they learned in 2nd grade (3.NBT.2). Last, the unit culminates in a synthesis of all learning thus far in the unit, in which students solve one and twostep word problems involving addition and subtraction and use rounding to assess the reasonableness of their answer (3.OA.8), connecting the NBT and OA domains. These skills are developed further and built upon in subsequent units in which students estimate and solve twostep word problems that also involve multiplication and division.
This builds toward an even deeper understanding of the place value system that students learn in 4th Grade Math. In 4th grade, students learn about multiplicative comparison, i.e., a value being x times as many as another value. Thus, students’ understanding of the place value system is more precisely refined as "a digit in one place represents ten times what it represents in the place to its right" (4.NBT.1, emphasis ours). Further, students learn to round any multidigit number to any place. They also use the standard algorithm to solve addition and subtraction problems to the new place values they encounter at this grade level, namely, to one million. While the majority of the content learned in this unit is additional cluster content, they are deeply important skills necessary to be proficient with the major work of the grade with 3.OA.8, as well as a foundation for rounding and the standard algorithms used to any place value learned in 4th grade (4.NBT.1—4) and depended on for many grade levels after that.
Pacing: 16 instructional days (14 lessons, 1 flex day, 1 assessment day)
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The following assessments accompany Unit 1.
Have students complete the PreUnit Assessment and PreUnit Student SelfAssessment before starting the unit. Use the PreUnit Assessment Analysis Guide to identify gaps in foundational understanding and map out a plan for learning acceleration throughout the unit.
Have students complete the MidUnit Assessment after lesson 7.
Use the resources below to assess student understanding of the unit content and action plan for future units.
Before you teach this unit, unpack the standards, big ideas, and connections to prior and future content through our guided intellectual preparation process. Each Unit Launch includes a series of short videos, targeted readings, and opportunities for action planning to ensure you're prepared to support every student.
pictorial or concrete base ten blocks 
Example: Represent 342 with base ten blocks.


place value chart 


number line 


standard algorithm for addition 

standard algorithm for subtraction 

tape diagram 
Example: A grocery store sells 172 red apples and 86 green apples. How many apples did the grocery store sell?

algorithm
approximate/approximation
approximately equal sign, $${\approx}$$
digit
estimate/estimation
place
reasonable
round
value
To see all the vocabulary for Unit 1, view our 3rd Grade Vocabulary Glossary.
Topic A: Foundations of Place Value
Topic B: Rounding to the Nearest Ten and Hundred
Topic C: Addition and Subtraction Within 1,000
Key
Major Cluster
Supporting Cluster
Additional Cluster
CCSS.MATH.PRACTICE.MP1 — Make sense of problems and persevere in solving them.
CCSS.MATH.PRACTICE.MP2 — Reason abstractly and quantitatively.
CCSS.MATH.PRACTICE.MP3 — Construct viable arguments and critique the reasoning of others.
CCSS.MATH.PRACTICE.MP4 — Model with mathematics.
CCSS.MATH.PRACTICE.MP5 — Use appropriate tools strategically.
CCSS.MATH.PRACTICE.MP6 — Attend to precision.
CCSS.MATH.PRACTICE.MP7 — Look for and make use of structure.
CCSS.MATH.PRACTICE.MP8 — Look for and express regularity in repeated reasoning.
Unit 2
Multiplication and Division, Part 1
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