COMMON CORE STANDARDS
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.
Add and subtract within 20.
2.OA.B.2 Fluently add and subtract within 20 using mental strategies. (See standard 1.OA.6 for a list of mental strategies.) By end of Grade 2, know from memory all sums of two one-digit numbers.
Use place value understanding and properties of operations to add and subtract.
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
MP.2 Reason abstractly and quantitatively.
MP.5 Use appropriate tools strategically.
MP.7 Look for and make use of structure.
MP.8 Look for and express regularity in repeated reasoning.
Operations and Algebraic Thinking
K.OA.A.3 Decompose numbers less than or equal to 10 into pairs in more than one way, e.g., by using objects or drawings, and record each decomposition by a drawing or equation (e.g., 5 = 2 + 3 and 5 = 4 + 1).
K.OA.A.4 For any number from 1 to 9, find the number that makes 10 when added to the given number, e.g., by using objects or drawings, and record the answer with a drawing or equation.
1.OA.A.5 Relate counting to addition and subtraction (e.g., by counting on 2 to add 2).
1.OA.A.6 Add and subtract within 20, demonstrating fluency for addition and subtraction within 10 Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
Number and Operations in Base 10
K.NBT.1 Compose and decompose numbers from 11 to 19 into ten ones and some further ones, e.g., by using objects or drawings, and record each composition or decomposition by a drawing or equation (e.g., 18 = 10 + 8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.
1.NBT.2 Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases:
1.NBT.B.2(a) 10 can be thought of as a bundle of ten ones—called a “ten.”
1.NBT.B.2(b) The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones.
1.NBT.C.4 Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, 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 and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
1.NBT.C.5 Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
1.NBT.C.6 Subtract multiples of 10 in the range 10–90 from multiples of 10 in the range 10–90 (positive or zero differences), 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 and explain the reasoning used.
DESCRIPTION OF UNIT
This Grade 2 Module 1 unit titled, “Sums and Differences to 100” developed by Eureka Math and cited on Engageny.org is intended to be completed in ten 60-minute sessions of mathematics instruction. This unit sets the foundation for students to master sums and differences to 20. Students then apply these skills to fluently add one-digit to two-digit numbers at least through 100 using place value understanding, properties of operations, and the relationship between addition and subtraction. Through unit activities, student skills advance to subtracting single-digit numbers from both multiples of ten. The summative assessment asks students to solve a variety of mathematical problems, as well as to write number sentences and statements in order to answer authentic application problems. The questions are designed to elicit direct, observable evidence of the degree to which a student can independently demonstrate the targeted standards.
Connecticut teachers should be cautioned that teacher notes and preparation materials are extensive and will require familiarity to be used effectively. Depending on the variability of students in the class, the foundational skills listed above for kindergarten and grade 1 may need to be reviewed before beginning this unit.
RATIONALE FOR SELECTION
This unit is an exemplary example of how to provide a balance between procedural skill, conceptual understanding and application. The unit plan focuses on the major work of the grade by extending students’ understanding of base-ten notation as they build fluency with addition and subtraction. Lessons are designed to build connections from previous work in earlier grades. Unit activities include fluency Sprints, application tasks based on real-life problems, discussion, observation, individual work, and regular formative assessments. A detailed daily instructional plan is included with notes on pacing and differentiated instruction. An aligned rubric for scoring the summative assessment is also included.
How to Implement A Story of Units—This resource provides details about EngageNY’s sequenced educational mathematics program for grades pre-K-5 with a strong emphasis on differentiating instruction, meaningful assessment, and data-driven instruction.
Scaffolding Instruction for English Language Learners Resource Guides for ELA and Mathematics—These guides provide guidance to educators on how to take the curriculum materials on EngageNY and provide additional scaffolds for ELLs.