Students build on their understanding of the structure of the place value system, start to use rounding as a way to estimate quantities, 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.
In the first unit of Grade 3, students will build on their understanding of the structure of the place value system from Grade 2 (MP.7), start to use rounding as a way to estimate quantities (3.NBT.1), as well as 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 Grade 2, 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, Grade 2 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 Grade 2, students are able to add and subtract within 1,000 but often aren’t relying on the standard algorithm to solve.
Thus, Unit 1 starts off with reinforcing some of this place value understanding of thousands, hundreds, tens, and ones being made up of 10 of the unit to its right that students learned in Grade 2. 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 students 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 Grade 2 (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 multiplication and division are added to the types of word problems students estimate and solve.
This builds toward an even deeper understanding of the place value system that students learn in Grade 4. In Grade 4, 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. Thus, while the majority of the content learned in this unit comes from an additional cluster, they are deeply important skills necessary to fully master 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 Grade 4 (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)
For guidance on adjusting the pacing for the 20212022 school year, see our 3rd Grade Scope and Sequence Recommended Adjustments.
This assessment accompanies Unit 1 and should be given on the suggested assessment day or after completing the unit.
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Pictorial or concrete base ten blocks 
Example: Represent 342 with base ten blocks. 
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? 
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whole
$${\approx}$$
endpoint
algorithm
value
round
reasonable
place
number line
interval
estimate/estimation
digit
approximate/approximation
To see all the vocabulary for this course, view our 3rd Grade Vocabulary Glossary.
With Fishtank Plus you can access our Daily Word Problem Practice and our contentaligned Fluency Activities created to help students strengthen their application and fluency skills.
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