Sample Unit of Focus Lessons: Subtraction Within 20 Grade: Primary

Sample Unit of Focus Lessons: Subtraction within 20 Grade: Primary

Monday Tuesday Wednesday Thursday Friday Counting backwards by Introducing subtraction Solving 1-digit by 1- Writing number models Solving subtraction 1s to a given number number models digit change-to-less for 1-digit by 1-digit number problems using stories change-to-less stories pennies and nickels using the symbols – and = Counting forward and Subtracting on the Counting forward and Finding missing Counting forward and backward on a number number line backward by 2s, 3s, 5s, numbers in a frames- backward on a calculator line and 10s and-arrows problem using +, - , and = symbols Solving number stories Acting out number Using addition and Using the Finding equivalent involving addition and stories involving subtraction to solve Addition/Subtraction names for numbers using subtraction addition and subtraction “What’s my rule?” Facts Table to find sums addition and subtraction problems of 1-digit whole numbers Learning about Writing fact families for Using fact triangles to Using the Using addition to check addition/subtraction fact dominoes see the relationship Addition/Subtraction answers for subtraction families between addition and Table to find sums and facts subtraction differences Finding values with sets Solving coin problems Making exchanges Making dollar Solve and record money of coins between coins exchanges number stories and solutions Making change Spending ten dollars Using a number grid to Using a number grid to Sharing strategies used subtract 1s and 10s from solve subtraction to subtract 2-digit 2-digit numbers problems numbers Solve number stories Write subtraction Determining the Subtracting multiples of Using mental math to involving subtraction of number sentences using unknown number in a ten in the range of 10-90 find 10 more and 10 less 2-digit numbers – and = subtraction equation in the range of 10-90

Note: Lessons highlighted in pink illustrate Everyday Math integration from EM Teacher’s Guide November 2012 Unit Resources

End of Unit Outcomes At end of this unit students will be able to:

(2011 MA Curriculum OA1. Use addition and subtraction within 20 to solve word problems involving situations of adding to, Framework for Mathematics) taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.1 OA3. Apply properties of operations as strategies to add and subtract.2 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.) OA4. Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8. OA5. Relate counting to addition and subtraction (e.g., by counting on 2 to add 2). OA6. Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use mental 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). OA7. Understand the meaning of the equal sign, and determine if equations involving addition and subtraction are true or false. For example, which of the following equations are true and which are false? 6 = 6, 7 = 8 – 1, 5 + 2 = 2 + 5, 4 + 1 = 5 + 2. OA8. Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 =  – 3, 6 + 6 = . MA.9. Write and solve number sentences from problem situations that express relationships involving addition and subtraction within 20. NBT1. Count to 120, starting at any number less than 120. In this range, read and write numerals and represent a number of objects with a written numeral.

Note: Lessons highlighted in pink illustrate Everyday Math integration from EM Teacher’s Guide November 2012 NBT2. Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: a. 10 can be thought of as a bundle of ten ones—called a “ten.” b. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones. c. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones). NBT4. 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. NBT5. Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used. NBT6. 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. Mathematical Practices By the end of this unit, students will be able to:

1. Make sense of problems and persevere in solving them. 2. Reason abstractly and quantitatively. 3. Construct viable arguments and critique the reasoning of others. 4. Model with mathematics. 5. Use appropriate tools strategically. 6. Attend to precision. 7. Look for and make use of structure. 8. Look for and express regularity in repeated reasoning.

Note: Lessons highlighted in pink illustrate Everyday Math integration from EM Teacher’s Guide November 2012 Sample List of Integrated  2.12 Subtraction Number Models Everyday Math Lessons  2.13 Number Stories (From Grade 1 Teacher’s Guide)  3.5 Counting on the Number Line For adaptation as focus lessons  5.8 Solving Number Stories in this unit  5.12 What’s My Rule?  6.1 The Addition/Subtraction Facts Table  6.2 Equivalent Names  6.3 Fact Families  6.4 Fact Triangles  6.5 Using the Facts Table for Subtraction  8.1 Review: Money  8.2 Dollars  8.4 Shopping at the School Store  8.5 Making Change  9.2 Adding and Subtracting Tens  9.4 Adding and Subtracting 2-Digit Numbers Everyday Math Games  2.13 Coin Top-It For use during Independent  3.6 Bunny Hop Problem-Solving connected to  5.7 Difference Game this unit  6.5 Penny Plate  8.1 Coin Exchange  8.2 One Dollar Exchange  8.5 3, 2, 1 Game  9.2 Number Grid Game

Note: Lessons highlighted in pink illustrate Everyday Math integration from EM Teacher’s Guide November 2012