• # Elementary Mathematics Grade 2 Unit 3

Subject: Mathematics
Timeline: 14 days
Unit 3 Title: Addition and Subtraction

Unit Overview:

This unit will give the opportunity for students to explore addition and subtraction.  Students will be exposed to addition strategies such as double facts, turn around facts, the + 9 shortcut and addition stories.   Students will also be introduced to strategies for subtraction such as the counting up and back strategies, the -0,-1, -8 and -9 shortcut strategies.  Lastly, they will be introduced to addition and subtraction fact families, name collection, and frames and arrows.

Unit Objectives:

At the end of this unit, all students must be able to utilize double facts, turn around facts and + 9 shortcut.Students must also be able to utilize subtraction strategies.  They must demonstrate knowledge of addition and subtraction fact families, name collection, and frames and arrows to become fluent with addition and subtraction.

Focus Standards:

PA.CCSS.Math.Content.CC.2.2.2.A.2 Use mental strategies to add and subtract within 20. (2.OA.1, 2.OA.2)
PA.CCSS.Math.Content.CC.2.1.2.B.2 Use place value concepts to read, write and skip count to 1000. (2.NBT.2)

Mathematical Practice Standards:

#1 Make sense of problems and persevere in solving them.

Mathematically proficient students start by explaining to themselves the meaning of a problem and look for an entry point to its solution.  They then plan a solution pathway rather than jumping into a solution attempt.  They monitor and evaluate their progress and change course, if needed.  Students might rely on using concrete objects or pictures to help conceptualize and solve a problem.  They then check their answers to problems using a different method, and continually ask themselves, “Does this make sense?”  These students can also understand the approaches of others to solving complex problems and identify correspondences between different approaches.

#4 Model with mathematics.

Mathematically proficient students can apply the mathematics they know to solve problems arising in everyday life, society, and the workplace. In early grades, this might be as simple as writing an addition equation to describe a situation.

#5 Use appropriate tools strategically.

Mathematically proficient students consider the available tools when solving a mathematical problem. These tools might include pencil and paper, concrete models, a ruler, a protractor, or a calculator. Proficient students are sufficiently familiar with tools appropriate for their grade to make sound decisions about when each of these tools might be helpful, recognizing both the insight to be gained and their limitations.

#6 Attend to Precision.

Mathematically proficient students try to communicate precisely to others.  They use clear definitions in discussions with others and in their own reasoning. They state the meaning of the symbols they choose, including the equals sign, consistently and appropriately.  They calculate accurately and efficiently and give carefully formulated explanations to each other.

Concepts - Students will know:
• How addition number models represent equivalence
• There are ways to solve addition problems mentally
• There are ways to solve subtraction problems mentally
• Word problems may involve both addition and subtraction in one problem
Competencies -Students will be able to:
• Add within 20 using short cuts strategies
• Subtract within 20 using short cut strategies
• Solve one-or two-step word problems involving addition or subtraction or both

Assessments:
• Unit 3 Progress Check and Exit Slips (Quizzes)
• Daily RSA

Elements of Instruction:

Expect to use differentiation options for students who may not have mastery of these skills.  First Grade Common Core State Standards for Numbers and Operations in Base-10 state; students will demonstrate that a bundle of ten ones is a group called a ten.  Students will use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing with unknown in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.  Students will understand apply properties of operation strategies to add and subtract.  Examples: If 8+3=11 is known, then 3+8=11 is also known. (Commutative property of addition.)  To add 2+6+4, the second two numbers can be added to make a ten, so 2+6+4=2+10=12. (Associative property of addition).

Differentiation:

Each lesson has differentiation options for each portion of the lesson.  Additional differentiation options are listed with directions and student masters in the Teacher’s Guide to Games.

Interdisciplinary Connections:
• Program related literature books and daily math routines.