Students add and subtract within 1,000 using strategies based on place value, properties of operations, and the operational relationship between addition and subtraction in order to add and subtract within 1,000. Students will use these strategies to add up to two 3digit numbers concretely, pictorially and abstractly and explain why these strategies work.
Math
Unit 5
2nd Grade
In Unit 5, 2nd grade students build on their addition and subtraction work from adding and subtracting two 2digit numbers and patterns within 10 to develop and use strategies to add and subtract within 1,000. By the end of 2nd grade students are expected to have a plethora of strategies and generalizable methods in order to add and subtract 3digit numbers within 1,000 (2.NBT.B.7). In this unit, students are introduced to adding and subtracting 3digit numbers within 1,000 using the standard algorithm, however students are not expected to be fluent or show proficiency with the standard algorithm until Grade 4. By extending their adding and subtracting work within 100 from Unit 2, students will use some of the strategies and understandings in their work within 1,000. This helps students with their work throughout their grade 2 mathematics and beyond.
In Topic A, students begin the unit by adding multiples of tens or hundreds. This is a continuation of the work done in Unit 2 where they added multiples of tens fluently within 100. Similarly, they also build off their Unit 1 and 2 work by applying strategies of compensation to adding threedigit numbers in order to get to a benchmark hundred.
Topic B focuses on methods for adding within 1,000. In this topic students use concrete manipulatives to represent their addition work. From there, they use their knowledge of concrete models to draw pictorial representations. Then finally, students move to more abstract representations, including the standard algorithm. Students use their knowledge of hundreds, tens, and ones as they show up to two compositions of a new hundred and a new ten.
In Topic C, students begin the topic by subtracting multiples of tens or hundreds. As similar work was completed in Topic A of this unit, students will also maintain a constant difference in order to subtract without needing to regroup.
In Topic D, students focus on subtraction within 1,000 and similarly move through concrete representations to pictorial, using place value drawings, and later more abstract representations to solve. Students use their place value knowledge to subtract with up to two decompositions of a hundred into 10 tens and ten into 10 ones in order to subtract in situations where there are not enough tens or ones. Students also explore how they can relate subtraction to addition in order to subtract as well as continue to practice abstract adding using the standard algorithm to check their work.
Finally, in Topic E students build on their work with word problems by solving more difficult problem types of onestep story problems as well as harder subtypes of twostep story problems. They build on their Unit 1 word problem work by continuing to use tape diagrams to represent the problem and using symbols to represent the unknown in their equations. They also use their knowledge of solving twice for twostep story problems from Unit 4 (2.OA.A.1). By the end of second grade students should be proficient in twostep word problem combinations of two middle difficulty problem types with addition and subtraction. Also, in this topic students will use their skills of making new hundreds in the context of adding up to four twodigit numbers and going beyond 100 (2.NBT.B.6) and explain the strategies they used to solve addition and subtraction problems (2.NBT.B.9).
The work students explore in this unit provides them with a better understanding of numbers and patterns first brought on in the foundation for their work in Unit 2. Students will continue to practice their fluency with 100 throughout their 2nd grade work as they continue to solve word problems within 100.
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The following assessments accompany Unit 5.
Have students complete the MidUnit Assessment after lesson 10.
Use the resources below to assess student understanding of the unit content and action plan for future units.
Read pp. 5863 on Number and Operation in Base Ten in the Progressions.
concrete base ten blocks 
134 shown in base ten blocks

pictorial base ten blocks 
368 + 106 = ?

place value chart 

number line 
545 + 30 = ?

arrow notation 
529 + 40 = ?

expanded form notation  $$\begin{array}{crcrcrcc} &400&+ &30&+ &5 &&&\\ + \ \ \ &200&+ &70 &+ &3 &&&\\ \hline &600&+ &100&+ &8 &= &708\end{array}$$ 
totals below for addition 

totals below for subtraction  $$ \begin{array}{cccccccc} &\overset{300}{\cancel{400}} &+ &\overset{110}{\cancel{10}} &+ &6 &&&\\  \ \ \ &100 &+ &80 &+ &40 &&&\\ \hline &200 &+ &30 &+ &2 &= &232 \end{array}$$ 
standard algorithm for addition 

standard algorithm for subtraction 

tape diagram 
Example: Armando buys 16 peppers for a barbecue. 7 of the peppers are red and the rest of the peppers are orange. How many orange peppers did Armando buy?

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
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 4
Place Value with Numbers to 1,000 & Money
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