Unit 4

Addition and Subtraction Within 200 with Word Problems to 100

 

Grade 2

Math

Unit Length and Description:

 

9 weeks

 

In Unit 4, students apply their work with place value units to develop conceptual understanding of addition and subtraction within 1000 moving from concrete to pictorial to abstract. Students deepen their understanding of base-ten, place value, and the properties of operations. They apply their knowledge to one-step and two-step word problems. During this unit, students also continue to develop one of the required fluencies of the grade: addition and subtraction within 100.

 

Standards:

 

Major Cluster: NBT – Number and Operation in Base Ten

Understand place value.

2.NBT.5

Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

2.NBT.6

Add up to four two-digit numbers using strategies based on place value and properties of operations.

2.NBT.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. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

2.NBT.8

Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.

2.NBT.9

Explain why addition and subtraction strategies work, using place value and the properties of operations.

Major Cluster: OA: Operations and Algebraic thinking

Represent and solve problems involving addition and subtraction.

2. OA.1

Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.

Standards for Mathematical Practice: Should be evident in every lesson.

MP.1 Make sense of problems and persevere in solving them. Students solve two-step word problems and are challenged to make sense of more complex relationships within situations. They flexibly solve problems with a variety of strategies at their disposal, sometimes finding many ways to solve the same problem.

MP.2 Reason abstractly and quantitatively. Students reason abstractly when they represent two-step problems and harder problem types with drawings such as tape diagrams and when they relate those drawings to equations. As the module progresses, students move back and forth between concrete, pictorial, and abstract work to make sense of quantities and their relationships in problem situations.

MP.3 Construct viable arguments and critique the reasoning of others. Students construct viable arguments when they use place value reasoning and properties of operations to explain why their addition and subtraction strategies work and when they use that reasoning to justify their choice of strategies in solving problems. They critique the reasoning of others when they use those same concepts to disprove or support the work of their peers.

MP.4 Model with mathematics. Students model with mathematics when they write equations to solve two-step word problems, make math drawings when solving a vertical algorithm, or when they draw place value charts and disks to represent numbers.

MP.6 Attend to precision. Students attend to precision when they label their math drawings and models with specific place value units. They calculate accurately and efficiently when adding numbers within 200 and when using the relationship between addition and subtraction to check their work.

Standards:  Instructional Outcomes

 

2.NBT.5: Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

  • I can identify the order in which to add three-digit numbers. (e.g. adding right to left)
  • I can identify properties of operations to add. (e.g. associative and commutative properties)
  • I can identify properties of operations to subtract. (e.g. associative and commutative properties)
  • I can identify when to regroup for addition and subtraction. (e.g. carrying and borrowing).
  • I can identify the order in which to subtract three-digit numbers. (e.g. subtracting right to left)
  • I can solve an addition and subtraction problem within 100 using a selected strategy.
  • I can add and subtract within 100 fluently.

 

2.NBT.6: Add up to four two-digit numbers using strategies based on place value and properties of operations.

  • I can identify strategies for adding up to four two-digit numbers based on place value.
  • I can identify strategies for adding up to four two-digit numbers based on properties of operations.
  • I can use strategies to add up to four two-digit numbers.

 

2.NBT.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. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

  • I can choose an appropriate strategy for solving an addition or subtraction problem within 1000.
  • I can explain how the strategy was used to write the equation.
  • I can compose hundreds and tens when necessary to add within 1000 (e.g. regrouping).
  • I can decompose hundreds and tens when necessary to subtract within 1000 (e.g. regrouping).

 

2.NBT.8: Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.

  • I can apply knowledge of place value to mentally add 10 to a given number 100-900.
  • I can apply knowledge of place value to mentally add 100 to a given number 100-900.
  • I can apply knowledge of place value to mentally subtract 10 from a given number 100-900.
  • I can apply knowledge of place value to mentally subtract 100 from a given number 100-900.

2.NBT.9: Explain why addition and subtraction strategies work, using place value and the properties of operations.

·         I can explain why addition strategies based on place value work.

·         I can explain why addition strategies based on properties of operations work.

·         I can explain why subtraction strategies based on place value work.

·         I can explain why subtraction strategies based on properties of operations work.

 

2. OA.1: Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem.

·         I can identify the number of steps to solve a word problem.

·         I can identify an unknown number in an equation using addition and subtraction up to 100.

·         I can identify the strategy/strategies for solving word problems. (Is it addition or subtraction?)

·         I can use addition and/or subtraction to solve 2 step word problems (equations) within 100.

 

Enduring Understandings:

 

·         When one quantity is joined or added on to another quantity, the result is greater than or equal to the initial quantity.

•   When one quantity is removed from another quantity, the result is less than or equal to the initial quantity.

·     Joining, removing, part-part-whole, and comparing problems can be modeled.

·     Addition and subtraction can be composed and decomposed to simplify the operation.

·     Mental math strategies may be used to solve problems involving numbers.

·         Problems and solutions can use various representations, including concrete objects, pictures, number sentences, and words.

Essential Questions:

 

·         How do we use addition and subtraction to tell number stories?

·         How does using ten as a benchmark number help us add and subtract?

·         How can we solve addition problems?

·         How can we solve subtraction problems?

·         How can strategies help us when adding and subtracting?

·         How are addition and subtraction alike and how are they different?

·         How are problem-solving strategies alike and different?