Whole Numbers
Whole numbers are the set of numbers that includes all the natural numbers (1, 2, 3, ...) and the number 0. They do not include any fractions or decimals.
Whole numbers are used for counting and ordering, and they can also be used in basic arithmetic operations such as addition, subtraction, multiplication, and division.
Examples of whole numbers include 0, 1, 2, 3, 4, 5, and so on.
Whole numbers are represented on the number line as evenly spaced points, with 0 as the starting point and the positive whole numbers extending to the right.
.◂Math Worksheets and Study Guides Second Grade. One More, One Less
Study Guide
One More, One Less 
Worksheet/Answer key
One More, One Less Worksheet/Answer key
One More, One Less Worksheet/Answer key
One More, One Less Vocabulary/Answer key
One More, One Less
Worksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyVocabulary/Answer keyThe resources above cover the following skills:
Number and Operations (NCTM)
Understand numbers, ways of representing numbers, relationships among numbers, and number systems.
Develop a sense of whole numbers and represent and use them in flexible ways, including relating, composing, and decomposing numbers.
Connect number words and numerals to the quantities they represent, using various physical models and representations.
Compute fluently and make reasonable estimates.
Develop and use strategies for whole-number computations, with a focus on addition and subtraction.
Develop fluency with basic number combinations for addition and subtraction.
Algebra (NCTM)
Use mathematical models to represent and understand quantitative relationships.
Model situations that involve the addition and subtraction of whole numbers, using objects, pictures, and symbols.
Grade 2 Curriculum Focal Points (NCTM)
Number and Operations and Algebra: Developing quick recall of addition facts and related subtraction facts and fluency with multi-digit addition and subtraction
Children use their understanding of addition to develop quick recall of basic addition facts and related subtraction facts. They solve arithmetic problems by applying their understanding of models of addition and subtraction (such as combining or separating sets or using number lines), relationships and properties of number (such as place value), and properties of addition (commutativity and associativity). Children develop, discuss, and use efficient, accurate, and generalizable methods to add and subtract multi-digit whole numbers. They select and apply appropriate methods to estimate sums and differences or calculate them mentally, depending on the context and numbers involved. They develop fluency with efficient procedures, including standard algorithms, for adding and subtracting whole numbers, understand why the procedures work (on the basis of place value and properties of operations), and use them to solve problems.