Unit 2

Addition and Subtraction of Two-Digit Numbers

Grade 2

Math

Unit Length and Description:

25 Days

Unit 2 helps students fluently add and subtract within 100 using strategies of properties of operations and relationships between addition and subtraction.  They will use addition and subtraction to solve word problems by using drawings and equations with a symbol for the unknown number to represent the problem.

Standards:

 OA - Operations and Algebraic Thinking Represent and solve problems involving addition and subtraction. 2.OA.A.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. NBT – Number and Operation in Base Ten 2.NBT.B.5 Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction. Standards for Mathematical Practice 1. Make sense of problems and persevere in solving them. 2. Reason abstractly and quantitatively. 3. Construct viable arguments and critique the reasoning of others. 4. Model with mathematics. 5. Use appropriate tools strategically. 6. Attend to precision. 7. Look for and make use of structure. 8. Look for and express regularity in repeated reasoning. Instructional Outcomes 2.OA.A.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.   2.NBT.B.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 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 compose and decompose for addition and subtraction using 2-digits. ·         I can solve an addition and subtraction problem within 100 using a selected strategy. ·         I can add and subtract within 100 fluently.

Enduring Understandings:

·         I can relate addition and subtraction to length using different strategies.

·         I can measure accurately using different measuring tools.

·         I can create mental benchmarks for measuring.

·         I can measure and compare to determine how much longer one object is than another.

Essential Questions:

·         How are addition and subtraction related to length using different strategies?

·         How can I measure accurately using different measuring tools?

·         What mental benchmarks for measuring do I use?

·         How do I compare to determine how much longer one object is than another?