Unit 2: Becoming Fluent With Addition and Subtraction
Overview by the Georgia Department of Education: In this unit students will: • cultivate an understanding of how addition and subtraction affect quantities and are related to each other • will reinforce the multiple meanings for addition (combine, join, and count on) and subtraction (take away, remove, count back, and compare) • further develop their understanding of the relationships between addition and subtraction • recognize how the digits 0-9 are used in our place value system to create numbers and manipulate amounts • continue to develop their understanding solving problems with money • At the beginning of Unit 2, it is recommended that students practice counting money collections daily during Number Corner or as part of daily Math Maintenance in order to be prepared for the tasks. For more detailed information regarding unpacking the content standards, unpacking a task, math routines and rituals, maintenance activities and more, please refer to the grade level overview. As students in second grade begin to count larger amounts, they should group concrete materials into tens and ones to keep track of what they have counted. This is the introduction of our place value system where students must learn that the digits (0-9) have different values depending on their position in a number. Students in second grade now build on their work with one-step problems to solve two-step problems. Second graders need to model and solve problems and represent their solutions with equations. The problems should involve sums and differences less than or equal to 100 using the numbers 0 to 100. Picture Graphs and Bar Graphs are also introduced in second grade. Investigations and experiences with graphing should take place all year long.
STANDARDS FOR MATHEMATICAL CONTENT Represent and solve problems involving addition and subtraction.
MGSE2.OA.1 Use addition and subtraction within 100 to solve one and two step word problems by using drawings and equations with a symbol for the unknown number to represent the problem. Problems include contexts that involve adding to, taking from, putting together/taking apart (part/part/whole) and comparing with unknowns in all positions. Add and subtract within 20.
MGSE2.OA.2 Fluently add and subtract within 20 using 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.
MGSE2.NBT.5 Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction. Work with time and money.
MGSE2.MD.8 Solve word problems involving dollar bills, quarters, dimes, nickels, and pennies, using $ and ¢ symbols appropriately. Example: If you have 2 dimes and 3 pennies, how many cents do you have? Represent and interpret data
MGSE2.MD.10 Draw a picture graph and a bar graph (with single-unit scale) to represent a data set with up to four categories. Solve simple put-together, take-apart, and compare problems 1 using information presented in a bar graph
BIG IDEAS By the conclusion of this unit, students should be able to demonstrate the following competencies: • Represent and solve problems involving addition and subtraction. • Solve a variety of word problems involving money using $ and ¢ symbols. • Understand and apply properties of operations and the relationship between addition and subtraction. • Recognize how the digits 0-9 are used in our place value system to create numbers and manipulate amounts. • Understand how addition and subtraction affect quantities and are related to each other. • Know the multiple meanings for addition (combine, join, and count on) and subtraction (take away, remove, count back, and compare) • Use the inverse operation to check that they have correctly solved the problem. • Solve problems using mental math strategies. • Draw and interpret picture and bar graphs to represent a data set with up to four categories.
Essential Questions • How do we represent a collection of objects using tens and ones? • How do I express money amounts? • When will estimating be helpful to us? • How can we use skip counting to help us solve problems? • Can we change the order of numbers if we subtract? Why or why not? • Can we change the order of numbers when we add (or subtract)? Why or why not? • How can estimation strategies help us build our addition skills? • How do we use addition to tell number stories? • How can benchmark numbers help us add? • How does using ten as a benchmark number help us add and subtract? • What strategies can help us when adding and subtracting with regrouping? • What strategies will help me add multiple numbers quickly and accurately? • How can we solve addition problems with and without regrouping? • How can addition help us know we subtracted two numbers correctly? • How can we solve subtraction problems with and without regrouping? • How can strategies help us when adding and subtracting with regrouping? • How can we model and solve subtraction problems with and without regrouping? How can mental math strategies, for example estimation and benchmark numbers, help us when adding and subtracting with regrouping? • How can I use a number line to help me model how I combine and compare numbers? • How are addition and subtraction alike and how are they different? • What is a number sentence and how can I use it to solve word problems? • How do we solve problems in different ways? • How can we solve problems mentally? What strategies help us with this? • How can we show/represent problems in different ways?