School Improvement in Maryland

Gr. 2 Unit: Add & Subtract within 20

Unit Overview

In this unit, students build upon the extended experiences with addition and subtraction in Kindergarten and Grade 1. In Grade 2, this study culminates with students becoming fluent in single-digit additions and related subtractions to 20 using the mental Level 2 and 3 strategies as needed. These strategies are listed on page 36 of the K, Counting and Cardinality; K-5 Operations and Algebraic Thinking Progressions of the Common Core which can be accessed at http://commoncoretools.files.wordpress.com/2011/05/ccss_progression_cc_oa_k5_2011_05_302.pdf. These mental strategies include Counting On, Recomposing Addends, and Doubles ± a number. It is the expectation that students were fluent within 5 in Kindergarten and then within 10 in Grade 1. Fluency involves a mixture of just knowing some answers, knowing some answers from patterns (e.g., adding 0 yields the same number), and knowing some answers from the use of strategies. Building fluency requires a combination of experiences that develop conceptual understanding as well as allow for practice in a variety of ways. Games and the use of concrete materials are an important part of these experiences.

Essential Questions:

  • Why do I need mathematical operations?
  • How do I know which mathematical operations to use?
  • What are different ways to count?
  • What are the most efficient ways to count?
  • In what ways can numbers be composed and decomposed?
  • What questions can be answered using addition and/or subtraction?
  • How are addition and subtraction related?
  • How can I use what I know about addition to help me subtract?

A question is essential when it stimulates multi-layered inquiry, provokes deep thought and lively discussion, requires students to consider alternatives and justify their reasoning, encourges re-thinking of big ideas, makes meaningful connections with prior learning, and provides students with opportunities to apply problem-solving skills to authentic situations.

Unit Lesson

Additional information such as Teachers Notes, Enduring Understandings,Content Emphasis by Cluster, Focus Standards, Possible Student Outcomes, Essential Skills and Knowledge Statements and Clarifications, and Interdisciplinary Connections can be found in this Lesson Unit.

Available Model Lesson Plans

The lesson plan(s) have been written with specific standards in mind. Each model lesson plan is only a MODEL - one way the lesson could be developed. We have NOT included any references to the timing associated with delivering this model. Each teacher will need to make decisions related ot the timing of the lesson plan based on the learning needs of students in the class. The model lesson plans are designed to generate evidence of student understanding.

This chart indicates one or more lesson plans which have been developed for this unit. Lesson plans are being written and posted on the Curriculum Management System as they are completed. Please check back periodically for additional postings.

CCSC Alignment: 2.OA.B.2

Students apply Level 2 & 3 strategies such as Counting On, Recomposing Addends, and Doubles ± a number when adding and/or subtracting. They demonstrate fluency for addition and subtraction within 20. They play a game in which they decide when it is best to Make Ten.

Available Model Lesson Seeds

The lesson seed(s) have been written with specific standards in mind. These suggested activity/activities are not intended to be prescriptive, exhaustive, or sequential; they simply demonstrate how specific content can be used to help students learn the skills described in the standards. Seeds are designed to give teachers ideas for developing their own activities in order to generate evidence of student understanding.

This chart indicates one or more lesson seeds which have been developed for this unit. Lesson seeds are being written and posted on the Curriculum Management System as they are completed. Please check back periodically for additional postings.

CCSC Alignnment: 2.OA.B.2

Students play a number cube game in which they apply their strategies to find the sums or differences.