FOCUS. COHERENCE Thinking Across Grades

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1 What's the Math? FOCUS Common Core State Standards Domain: Operations and Algebraic Thinking Major Cluster: Use place value understanding and properties of operations to add and subtract. Objective: Students will subtract one-digit numbers from two-digit numbers. Standards 2.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. Also addresses: 2.OA.1, 2.NBT.9 The content in this lesson addresses a standard from the Number and Operations in Base Ten domain, while the content of this chapter overall addresses standards from the Operations and Algebraic Thinking domain. Standards from different domains are sometimes closely related. Mathematical Practices 1 Make sense of problems and persevere in solving them. 2 Reason abstractly and quantitatively. 4 Model with mathematics. 5 Use appropriate tools strategically. 6 Attend to precision. 8 Look for and express regularity in repeated reasoning. COHERENCE Thinking Across Grades Previous Grade 1 1.OA.6 Now Grade 2 2.NBT.5 Next Grade 3 3.NBT.2 Linking to Major Topics Connected to the following critical areas of focus: 2. Building fluency with addition and subtraction. 1. Extending understanding of base-ten notation. Connected to the following standards: 1.NBT.2, 2.OA.1, 2.NBT.7, 3.NBT.2 RIGOR The exercises increase in complexity throughout the lesson. However, individual student thinking may vary during extended processing. Levels of Complexity Level 1 Understand Concepts Exercises 1 2 Level 2 Apply Concepts Exercises 3 14 Level 3 Extend Concepts Exercises 15 17; HOT Problem What Students Should Understand Printed by: Angie Ward Page 1 of 11 Printed on 01/12/2015 6:54 PM

2 When subtracting with two-digit numbers, subtract the ones and then the tens. Regroup 1 ten as 10 ones as needed. What Students Should Be Able To Do Find Building on the Essential Question In this lesson, students will build upon the skills and concepts needed to answer the chapter s Essential Question How can I subtract two-digit numbers? Common Core Quick Check, Chapter 4, Answer Key, Common Core Quick Check, Chapter 4, Printed by: Angie Ward Page 2 of 11 Printed on 01/12/2015 6:54 PM

3 Developing Vocabulary / Get Ready Review Vocabulary/Cognate regroup/reagrupar tens ones Activity Draw the number line shown below on the board. Remind students that they have already learned to subtract on a number line. Ask students how they would use the number line to find Students should explain that they would start at 32 and count back 3 to find that 32 3 is 29. Erase the number line. Write 32 3 on the board. Attend to Precision What is another way to solve the problem 32 3 besides using a number line? Explain. Sample answer: I could use base-ten blocks to solve the problem. I would show 32 base-ten blocks, and then take away 3. Then regroup to find the difference is 29. Discuss all of the different ways students could solve the problem. English Language Learner Instructional Strategy Sensory Support: Pictures/Photographs To introduce the lesson, use pictures of items in groups of 10 to practice counting as a class. Use pictures of the items named in the Lesson/Problem Solving exercises to clarify the terms: crabs, beach coins, machine, cafeteria, apples, lunch, store, shirts, and display. Pair emerging/expanding students with bilingual (same native language) bridging level students during the Problem Solving exercises. Allow use of native language to clarify meaning. For non-spanish speaking ELLs, refer to the Multilingual eglossary for interactive definitions in 13 languages. My Vocabulary Cards Have students use a blank card to summarize the steps used to regroup. Vocabulary Review, Grade 2 Printed by: Angie Ward Page 3 of 11 Printed on 01/12/2015 6:54 PM

4 Launch the Lesson / Investigate & Model Review Problem of the Day Use connecting cubes to model the number 7. Is the number 7 even or odd? odd Use the connecting cubes to show how you know. Answers will vary. Reason Quantitatively If you added one more connecting cube to the group of 7 cubes would the total number be even or odd? Explain. Sample answer: even; When I added on one more cube to the group, the total number of cubes is 8 and that is an even number. Common Core Quick Check Use this activity as a quick review and assessment of the previous lesson. A printable version is available online. Additional Literature Connection Read a trade book, such as Monster Musical Chairs by Stuart J. Murphy, to prepare students for this lesson. Investigate the Math Target: Conceptual Understanding Materials: Lesson Presentation slides This investigation emphasizes mathematical reasoning and mathematical processes. What steps do you use when subtracting one-digit numbers from two-digit numbers? Students investigate ways to model with math. Students come together to discuss their results and attend to precision. Model the Math Target: Procedural Skills and Fluency Materials: base-ten blocks, Work Mat 6 Prepare subtraction problems, some of which require regrouping and some that do not. Sample problems: 63 7, 75 4, 42 9, and Point to each problem, one at a time. Have students stand up if it is necessary to regroup. Have them raise their right hand if it is not necessary to regroup. Have students use base-ten blocks to prove their responses. Some students may benefit from using the Work Mat. Printed by: Angie Ward Page 4 of 11 Printed on 01/12/2015 6:54 PM

5 Problem of the Day, Grade 2, Chapter 4, Lesson 4 Answer Key, Problem of the Day, Grade 2, Chapter 4, Lesson 4 Place-Value Models Base Ten Blocks Investigate the Math, Grade 2, Chapter 4, Lesson 4 Printed by: Angie Ward Page 5 of 11 Printed on 01/12/2015 6:54 PM

6 Teach Explore and Explain You will need base-ten blocks Read the directions that are at the bottom of the student page. What do you need to find? The number of crabs left on the beach. How can you find this? Find Have students use the place-value chart to model the subtraction. Place 34 base-ten blocks on the place-value chart. Subtract the ones first. Can you take away 8 ones from 4 ones? no What do you do when there are not enough ones to subtract from? Sample answer: Regroup 1 ten as 10 ones. After regrouping, how many ones are there? 14 ones Are there enough ones to take away 8 ones? yes What is 14 ones - 8 ones? 6 ones Subtract the tens next. How many tens are left? 2 tens You have 2 tens and 6 ones left. What number does this equal? 26 So, 26 crabs were left on the beach. Have students draw the base-ten blocks that are left on the place-value chart. Model with Mathematics What number sentence could you write to solve this problem? 34-8 = 26 See and Show Guide students through the example at the top of the page. Repeated Reasoning Have students look at the See and Show box. Is it always true, sometimes true, or never true, that when subtracting a two-digit number you will need to regroup. Explain. Sample answer: It is sometimes true, that when you subtract a two-digit number you will need to regroup. If there are not enough ones to subtract, then you would need to regroup. Work through Exercises 1 2 together as a class. Talk Math: Collaborative Conversation Reason Quantiatively How do you regroup 1 ten? Sample answer: You make 10 ones out of 1 ten. Place-Value Models Place-Value WorkMat, 3-digit Virtual Manipulatives Subtract One-Digit Numbers from Two-Digit Numbers Printed by: Angie Ward Page 6 of 11 Printed on 01/12/2015 6:54 PM

7 Practice & Apply On My Own Based on your observations, you may choose to assign exercises as noted in the levels below: Approaching Level Guide students through the exercises in On My Own. Help them use manipulatives while working through the exercises. On Level Complete the exercises independently. Beyond Level Complete the exercises independently without manipulatives. Common Error! Help students understand that regrouping is necessary when there are not enough ones to subtract the bottom number from the top number. Problem Solving Persevere in Solving Problems Exercise 16 What if teachers buy 7 of the apples, now how many apples would be left? 22 apples Attend to Precision HOT Problem Tell students to explain their answer to a friend. Formative Assessment Strategy Form Have students consider what they have learned by writing a response to the following prompts. 3: Things that they learned today; 2: Things they want to know more about; 1: Questions they have. Self-Check Quiz: Subtract From a Two-Digit Number Fact Dash Printed by: Angie Ward Page 7 of 11 Printed on 01/12/2015 6:54 PM

8 Differentiated Instruction Differentiated Instruction Tier 2: Strategic Intervention Hands-On Activity Materials: connecting cubes If students cannot grasp the concept of subtracting from a two-digit number by using base-ten blocks, have them try using connecting cubes. Students can model tens with one color and ones with another color. Tier 1 Hands-On Activity Materials: newspapers, scissors, glue, construction paper Give each student a newspaper and a piece of construction paper. Have students cut out numbers from the newspaper. Tell students to make vertical subtraction problems by gluing the numbers on the construction paper. Have students find the differences. Tell students to cut out numbers and glue the differences on to the construction paper. Have students share their work and discuss how they solved one of their subtraction sentences with the class. Extend Hands-On Activity Materials: hundred charts, index cards with numbers Have students work in groups of three. The first student draws a card and locates the number on the hundred chart. Discuss how to round numbers. Then he or she rounds the number by finding the nearest ten. The second student repeats the process. The third student subtracts the smaller of the two rounded numbers from the larger number. Students continue, switching roles. Differentiated English Language Learner Support Background Knowledge Distribute base-ten blocks to students. Write 34-8 on the board. Then use base-ten blocks to model solving the problem with regrouping. Ask, Can I subtract the ones? Give students a chance to answer no, then say, No, first I need to regroup. Have students follow along with their own manipulatives as you finish solving the problem. Write examples and non-examples of two-digit subtraction problems that require regrouping. For each problem, ask, Do I regroup? Allow time to answer, confirm answers, and model solving the problem. Building Oral Language On index cards, write examples and non-examples of two-digit subtraction problems that require regrouping. Randomly distribute the cards to students. Have each student explain whether or not regrouping is required. Provide sentence frames, such as: I need to regroup because. or I Printed by: Angie Ward Page 8 of 11 Printed on 01/12/2015 6:54 PM

9 do not need to regroup because. Then have students solve the problems on their cards. For a language extension, discuss the contraction don t for do not and have students utilize don t in the sentence frame. Partner Work Have students get into pairs. Have each pair decide which student will be One and which student will be Two. Then say, Ones will write a two-digit subtraction problem that does not need regrouping. Twos will write a two-digit subtraction problem that needs regrouping. If necessary, provide an example of each on the board. Then give students time to write their problems. Have the students in each pair exchange problems, solve them, and then provide feedback to each other about whether or not the problem met the requirement. Fact Dash Enrich Worksheet: Subtract From a Two-Digit Number Enrich Worksheet: Subtract From a Two-Digit Number, Answer Key Reteach Worksheet: Subtract From a Two-Digit Number Reteach Worksheet: Subtract From a Two-Digit Number, Answer Key Enrich Worksheet: Subtract From a Two-Digit Number Reteach Worksheet: Subtract From a Two-Digit Number Hundred Chart Number Cards Printed by: Angie Ward Page 9 of 11 Printed on 01/12/2015 6:54 PM

10 Wrap It Up My Homework Assign homework after successful completion of the lesson. Students who understand the concepts may skip the Homework Helper section. Problem Solving Use Appropriate Tools Exercise 11 What tools could you use to check your answer? Sample answer: I could use base-ten blocks to help me check my answer. Have students use the tool of their choice to check their answer. Test Practice Diagnose Student Errors Class trends in wrong answers may indicate common errors or misconceptions. 52 added instead of subtracted 44 subtracted incorrectly 33 subtracted incorrectly 34 correct Formative Assessment You will need: write-on/wipe-off boards dry erase markers Response Boards Pass out a write-on/wipe-off board and marker to each student. Write the following on the board for students to solve on their write-on/wipe-off boards Once each student has finished solving the problem, tell them to hold their boards in the air. My Homework, Chapter 4, Lesson 4 Answer Key, My Homework, Chapter 4, Lesson 4 Place-Value Models Printed by: Angie Ward Page 10 of 11 Printed on 01/12/2015 6:54 PM

11 Printed by: Angie Ward Page 11 of 11 Printed on 01/12/2015 6:54 PM