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Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Maryland College and Career-Ready Standards In this unit, students will build on their understanding of multiplication and division from grade 3. In the first part of the unit, students will extend their understanding of the base-ten system by recognizing that the value of each place is ten times the value of the place to the immediate right. Students will develop an understanding of multiples and factors, while applying their understanding of multiplication from grade 3. This understanding lays a strong foundation for generalizing strategies learned in previous grades. Students will be able to develop, discuss, and use efficient, accurate, and generalizable computational strategies involving multi-digit numbers. These concepts and the terms “prime” and “composite” are new to grade 4, so they are introduced early in the year to give students ample time to develop and apply this understanding. Students will also focus on building conceptual understanding of multiplication of larger numbers and division with remainders. Students should make connections between their conceptual understanding of place value developed in unit 1 with their understanding of multiplication and division. Place value models and area of rectangles can provide visuals and context for further developing these understandings. A strong understanding of the connection between multiplication and division with smaller numbers will help students understand division of larger numbers and make sense of remainders. Students should be able to apply alternative algorithms that make sense based on place value so that they can explain the reasonableness of their computation. These strategies will lay a strong foundation based in understanding of number and operation for when they are ready for the multiplication and division traditional algorithms in later grades. Research In the base-ten system, the value of each place is 10 times the value of the place to the immediate right. Because of this, multiplying by 10 yields a product in which each digit of the multiplicand is shifted one place to the left. Students need to develop an understanding of the concepts of number theory such as prime numbers and composite numbers. For students to develop an understanding of procedures for multiplying multi-digit numbers, area models and arrays are powerful representations. These models allow students to see why and how we multiply each place in one number by each place in another number. This is the big idea behind multi-digit multiplication, students should have opportunities to build and work with concrete manipulatives to build this understanding. It illustrates the distributive property of multiplication over addition. The distributive property uses known products to find unknown products. For example, 8 x 7 can be thought of as (8 x 5) + (8 x 2) = 40 + 16 = 56. An array shows the partial products resulting from separately multiplying the digits in the different place value positions. (Focus in Grade 4: Teaching with Curriculum Focal Points) To explore division with remainders, students should use familiar division models to solve non-basic fact division equations, such as 44 ÷ 7 = ___. After understanding the meaning of remainders, through the use of manipulatives and pictorial representations, students should be instructed to develop a sense of the “closest basic fact under” concept. For example, they might think 7 x 6 = 42 and 7 x 7 = 49. Since 49 is greater than 44, students realize that when 44 objects are divided equally among 7 groups, the largest whole number of objects that can be placed in each group is 6, and 2 objects are left over. Consequently, 7 x 6 = 42 is the “closest basic fact” of 7 “under” 44. (Focus in Grade 4: Teaching with Curriculum Focal Points) 1 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days The chart below highlights the key understandings of Unit 2 along with important questions that teachers should pose to promote these understandings. The chart also includes key vocabulary that should be modeled by teachers and used by students to show precision of language when communicating mathematically. Enduring Understandings Essential Questions Students will understand that: Place value helps determine relationships between numbers Estimation can be used to determine the reasonableness of an answer. Mathematical properties show number relationships and can be used to compute flexibly. Problems can be represented and solved accurately using a variety of strategies. Problems can be solved using multiplication and division. How does the value of a digit change when it is multiplied and divided by 10? How can patterns, strategies, and formulas help solve problems accurately? When is estimation more useful than finding a precise answer? Why is place value understanding important in multiplication and division? What is the relationship between multiplication and division? How can we use mathematical properties and/or rules to solve problems? What are factors? How are factors of a number determined? What does it mean for a number to be classified as either prime or composite? How are remainders and divisors related? What is the meaning of a remainder in a division problem? How do compatible numbers aid in dividing whole numbers? How can an understanding of representing multi-digit multiplication help in solving area problems? Key Vocabulary Commutative property Composite Distributive property (of multiplication over addition) Dividend Divisor Equation Even Expression Factor Factor pairs Multiple Odd Pattern Place value Prime Product Quotient Remainder Rule Sequence Term Value Variable Background Reading Focus in Grade 4: Teaching with Curriculum Focal Points Teaching StudentCentered Mathematics – Grades 3-5 Putting the Practices into Action: Implementing the Common Core Standards for Mathematical Practice K-8 2 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Throughout this cluster, students will develop their use of the 8 Mathematical Practices while learning the instructional standards. The mathematical practices in the shaded boxes should be emphasized during instruction of this unit due to how well they connect with the content standards in this unit. Standards for Mathematical Practice 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 Connections to this Cluster Solve problems in which the solution is not immediately evident. To determine and articulate what the problem is asking: Ask students to restate the problem in their own words. Have students turn to a partner to state the problem. Discuss familiar problems (When have we seen something like this before? What did we do?) To self-monitor progress and change directions when necessary: Have students talk or write about how they got “stuck” and then “unstuck” when solving a problem. Think aloud to show students how to change course when needed. To demonstrate perseverance in problem-solving and identify different ways to solve a problem: Make a classroom list of possible strategies. Acknowledge those who modify their thinking and persevere to get to the solution and have students show and talk about how they solved problems. Encourage students to show at least two ways to solve a problem. Write an equation for a situation and be able to explain how the equation relates to the situation presented. Solve the equation outside of the context of the problem, and then connect the solution back to the situation presented. To make sense of quantities and their relationships in problem situations: Represent a given multiplication and division situations problem with the equation using a variable for the unknown. Write a situation problem that matches a specific equation. Explain why a number is prime or composite, based on knowledge of factors. Justify a numeric pattern based on following a rule, and analyze and critique the reasoning of others. Provide multiple opportunities for students to explain, explore, record, and try student-invented strategies. Model how effective labeling communicates math reasoning. Discuss student representations and solution methods. -Ask students to restate and try peer methods for solving problems. -Help students make mathematical connections between different representations/solution methods. -Evaluate the efficiency of the strategies based on the probability of an error occurring. Write equations for various problem situations and solve problems about the situations. Represent the unknown with a variable. Represent problem situations in multiple ways including numbers, words (mathematical language), drawing pictures, using objects, and creating equations Connect the different representations and explain the connections. Evaluate their results in the context of the situation and reflect on whether the results make sense. 3 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days 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 Use manipulatives, area models, arrays, number lines (for estimation), and drawings that represent mathematical situations. Consider the available tools (including estimation) when solving a mathematical problem and decide when certain tools might be helpful. Explain how tools can assist them in seeing patterns and relationships with numbers. Create accurate drawings and representations of mathematical situations. Use specific math vocabulary to communicate mathematical ideas. Compute accurately. Develop and display anchor charts with precise math vocabulary. Orally rephrase student explanations using appropriate vocabulary. Look closely to discover a pattern or structure and apply the properties of operations to solve problems. Use properties of operations to perform and explain calculations (partial products model) with multi-digit numbers; provide opportunities in which students explore mathematical properties; and ask students to construct arguments to prove mathematical properties. Complete and describe number patterns with whole numbers. Explore patterns in different ways using hundred charts (prime and composite numbers) and multiplication charts. Use ratio tables to show the relationship between two pieces of data and to explore patterns and functions. such as in the following problem: Zoe was painting flowers on the classroom mural. Every flower had 6 petals. How many petals were on the mural after 8 flowers had been painted? Notice repetitive actions in computation and make generalizations about rules and “short-cuts” to get to answers more quickly. Use models to explain calculations and understand how algorithms work. Use models to examine patterns and generate alternative algorithms. 4 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Generalize place value understanding for multi-digit whole numbers. Maryland College and Career-Ready Standards 4.NBT.A.1 Recognize that in a multi-digit whole number, a digit in one place represents ten times what it represents in the place to its right. For example, recognize that 700 divided by 70 equals 10 by applying concepts of place value and division. This standard strengthens student’s understanding of place value related to multiplying and dividing by multiples of 10. Students reason about the magnitude of digits in a number. In the base-ten system, the value of each place is 10 times the value of the place to the immediate right. For example, in the number 2,443 the digit 4 in the hundreds place is worth ten times the digit 4 in the tens place. (400 is ten times 40, or conversely, 40 is ten times less than 400). In third grade, students explored multiplying a single-digit number by a multiple of ten (3.NBT.3). For example, when multiplying 8 x 10, the product of 8 x 1 is shifted one place to the left indicating 8 tens or 80. In fourth grade, students build on this understanding when interpreting and comparing the value of digits in multi-digit numbers. 4.NBT.A.1a How is the digit 7 in the number 3,784 different from and similar to the digit 7 in the number 7,843? 4.NBT.A.1b How are the numbers 24,019 and 20,914 alike? How are they different? Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000. SMP 7. Look for and make use of structure. Formative Assessments Instructional Strategies and Resource Support 4.NBT.A.1c (Progressions for the Common Core State Standards in Mathematics (draft), The Common Core Standards Writing Team, April 2012, p. 12) The amount of jelly beans in each jar is a five -digit number with the following digits: 2 9 7 5 3 5 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Generalize place value understanding for multi-digit whole numbers. Maryland College and CareerReady Standards 4.NBT.A.1 Recognize that in a multidigit whole number, a digit in one place represents ten times what it represents in the place to its right. For example, recognize that 700 divided by 70 equals 10 by applying concepts of place value and division. Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000. SMP 7. Look for and make use of structure. Instructional Strategies and Resource Support Students need varied opportunities to build multi-digit numbers in order to solidify understanding of the relationship between places in greater numbers. Base-ten blocks, Digiblocks, and place value disks are useful tools to help build numbers and compare values of digits. When comparing digits in 2 different numbers, students should be able to reason about the magnitude of the digits in relation to multiples of ten. For example, when comparing 5,368 and 2,643, students should recognize that the “6” in 5,368 is worth 10 times less than the “6” in 2,643. Additionally, the “3” in 5,368 is 100 times the value of the “3” in 2,643. Formative Assessments 4.NBT.A.1d Lauren worked at Slide and Splash Water Park over the summer. During her first week, she recorded the number of people who visited the park daily. Complete her log using the clues that follow. Day of the Week Number of Visitors Thursday Friday Saturday Sunday 2,945 4,163 Teaching Student-Centered Mathematics – Grades 3-5 “Numbers Beyond 1,000” - pp. 47-51 Activity 2.8 “What Comes Next?” (p.48) Lexi has 25 ten-dollar bills; Abbey has 25 hundred-dollar bills. Do they have the same amount of money? How many 10-dollar bills are equal to 15 hundred-dollar bills? Show your thinking. What if there was a thousand dollar bill, how many of those would be equal to 25 hundreddollar bills? 6 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Maryland College and CareerReady Standards Gain familiarity with factors and multiples. 4.OA.4 Find all factor pairs for a whole number in the range 1-100. Recognize that a whole number is a multiple of each of its factors. Determine whether a given whole number in the range 1-100 is a multiple of a given onedigit number. Determine whether a given whole number in the range 1-100 is prime or composite. NOTE: The focus of this standard is not necessarily to become fluent in finding all factor pairs, but to use student’s understanding of the concept and language to discuss the structure of multiples and factors. SMP 3. Construct viable arguments and critique the reasoning of others. 7. Look for and make use of structure. Instructional Strategies and Resource Support This standard requires students to demonstrate understanding of factors and multiples of whole numbers. A factor is a number that is multiplied by another number to create a product. Three and six are factors of 18. A multiple is the product of a whole number and any other whole number. Twenty is a multiple of four, because 4 x 5 = 20. Students should understand the process of finding factor pairs. Examples: Use visual models, such as an array with tiles or grid paper or a rectangular area model Factor tree Factor “rainbow” Formative Assessments 4.OA.B.4a 4 is a factor of two different numbers. What else might be true about both of the numbers? 4.OA.B.4b a. b. Factors of 18 – 1, 2, 3, 6, 9, 18 c. Multiples can be thought of as the result of skip-counting by each of the factors. When skip-counting, students should be able to identify the number of factors counted, e.g. 4, 8, 12, 16, 20, 24 – there are six 4’s in 24. Example: 4.OA.B.4c Use counters to determine if 51 is prime or composite. Multiples – 1, 2, 3, 4, … 18 2, 4, 6, 8, 10, 12, 14, 16, 18 3, 6, 9, 12, 15, 18 6, 12, 18 9, 18 18 4.OA.B.4d Students should be able to determine when they have made all possible arrays and listed all factor pairs for a number between 1 and 100. Teaching Student-Centered Mathematics – Grades 3-5 Make a list of the first ten multiples of 4. Which of the numbers in the list are multiples of 8? Describe the pattern you see where the multiples of 8 appear in the list. Which numbers in the list are multiples of 3? pp. 63-64 Evan is getting ready to make s’mores. He bought 2 bags of marshmallows. The bags each contain 36 marshmallows. Evan wants everyone to have the same amount of marshmallows and not have any left over. 7 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Maryland College and CareerReady Standards Gain familiarity with factors and multiples. 4.OA.4 Find all factor pairs for a whole number in the range 1-100. Recognize that a whole number is a multiple of each of its factors. Determine whether a given whole number in the range 1-100 is a multiple of a given onedigit number. Determine whether a given whole number in the range 1-100 is prime or composite. NOTE: The focus of this standard is not necessarily to become fluent in finding all factor pairs, but to use student’s understanding of the concept and language to discuss the structure of multiples and factors. Instructional Strategies and Resource Support Formative Assessments Through exploration with multiples of a number between 1 and 100, the following generalizations should emerge, as well as others: All even numbers are multiples of 2. All numbers that can be halved twice, with a whole number result, are multiples of 4. All numbers with a 0 or 5 in the ones place are multiples of 5. All numbers with a 0 in the ones place are multiples of 10. All numbers that are multiples of both 2 and 3 are also multiples of 6. Additionally, this standard refers to prime and composite numbers. Prime numbers have exactly two factors, the number one and itself. For example, the number 13 has the factors of 1 and 13. Composite numbers have more than two factors. For example, 9 has the factors 1, 3, and 9. A common misconception is that the number 1 is prime, when in fact; it is neither prime nor composite. Another common misconception is that all prime numbers are odd numbers. However, the number 2 (an even number) has only 2 factors: 1 and 2. To explore prime and composite numbers, build rectangular arrays and determine which numbers have more than two arrays. Examples: Rectangular Arrays for 8 Rectangular Arrays for 7 SMP 3. Construct viable arguments and critique the reasoning of others. 7. Look for and make use of structure. 1 x 7 OR 7 x 1 Prime: Exactly 2 factors: (1 and 7) 1 x 8 OR 8 x 1 2 x 4 OR 4 x 2 Composite: More than 2 factors: (1, 2, 4, and 8) 8 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Generate and analyze patterns. Maryland College and CareerReady Standards 4.OA.5 Generate a number or shape pattern that follows a given rule. Identify apparent features of the pattern that were not explicit in the rule itself. For example, given the rule “add 3” and the starting number 1, generate terms in the resulting sequence and observe that the terms appear to alternate between odd and even numbers. Explain informally why the numbers will continue to alternate in this way. NOTE: Although there are shape patterns in arrays, the focus of this unit is number patterns. 4.OA.5 will appear again in Unit 7 – Geometry and Patterns, where the focus will be on identifying shape patterns. SMP 3. Construct viable arguments and critique the reasoning of others. 7. Look for and make use of structure. Instructional Strategies and Resource Support Formative Assessments Teaching Student-Centered Mathematics – Grades 3-5 pp. 299-303 Students need many opportunities creating and extending number patterns. Numerical patterns allow students to reinforce basic facts, develop fluency with operations, and to be more analytical about number sequences and relationships. What’s Next and Why? (TSCM, Grades 3-5, p. 299) Show students five or six numbers from a number pattern. Then, have them extend the pattern for several more terms and explain the rule for generating the pattern. Examples: 1, 2, 4, 8, 16 … double the previous number 2, 5, 11, 23 … double the previous number and add 1 1, 2, 4, 7, 11 … successively add 1, then 2, then 3, and so on 0, 1, 5, 14, 30 … add the next square number 2, 2, 4, 6, 10, 16 … add the preceding two numbers Make up your own pattern or challenge students to create their own number pattern rule. Have students skip count starting at a number other than zero. Have them make conjectures and then determine why they are true. Example: 3, 8, 13, 18, 23, 28 When skip counting by 5 starting at 3, the ones place alternates between 3 and 8. This happens because 5 is half of 10, so a given term is ten more than 2 terms before it. When you add 10 to a number, the ones place stays the same. 4.OA.C.5a __ __ 16 __ __ Complete a number pattern above. What is the rule for your pattern? Identify at least two features of the pattern that are not part of the rule. 4.OA.C.5b Skip-count by 5’s beginning with the number 6. ____ , ____ , ____ , ____ , ____ , ____ , ____ , ____ What features do you notice in the pattern? Students should be able to identify common terms of two patterns and identify features of those common terms. For example, if skip counting by 4 and 8 starting at zero, all multiples of 8 are also multiples of 4. 9 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Use the four operations with whole numbers to solve problems. Maryland College and CareerReady Standards 4.OA.3 Solve multistep word problems posed with whole numbers and having wholenumber answers using the four operations, including problems in which remainders must be interpreted. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding. NOTE: This is the first time students are expected to interpret remainders based upon the context. All four operations will be addressed in Unit 5 – solving measurement problems, and the standard will be finalized at the end of the year. SMP 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. 6. Attend to precision. 7. Look for and make use of structure. Instructional Strategies and Resource Support This standard has multiple areas of focus: A. Solving multistep problems using a variety of strategies B. Using compatible numbers (numbers that sum to 10 or 100) or rounding in order to estimate a solution that is reasonable C. Interpreting remainders in division problems A. Students often believe that there is only one way to solve a problem and that a problem only has one solution. They need many opportunities to explore problems that can be solved using a variety of strategies and do not have an obvious answer. Encourage students to share problem-solving approaches in order to develop communication of reasoning and to assess efficiency of strategies. B. Problems should be structured so that all acceptable estimation strategies will arrive at a reasonable answer. Students need many opportunities solving multistep story problems. One aspect of fluency in whole-number multiplication is the ability to use estimation to approximate products and to determine the reasonableness of exact results. Encourage students to use rounding, patterns in powers of 10, and basic multiplication facts to accomplish this. Examples: 1. To estimate 427 x 8 , round 427 to 400, then multiply 400 x 8. 2. Extend facts that involve the patterns with zeros, e.g. 6 x 7, 60 x 7, 60 x 70. Focus in Grade 4: Teaching with Curriculum Focal Points Estimation and fluency in multiplication -- p. 20 SMP: Present solutions to multi-step problems in the form of valid chains of reasoning, using symbols such as equals signs appropriately (for example, rubrics award less than full credit for the presence of nonsense statements such as 12x2=24÷4=6 even if the final answer is correct), or identify or describe errors in solutions to multi-step problems and present corrected solutions. Formative Assessments 4.OA.A.3a There were 5 baseball players taking batting practice. They hit 85 balls all together. If each player hit the same number of baseballs, how many baseballs did 1 player hit? ______ 4.OA.A.3b There are five 4th grade classes in the gym for a science program about the Chesapeake Bay. Each class has 26 students. During the program, the students need to be in groups of 6 to complete Bay-themed activities. 4.OA.A.3c Lauren opened her dog-walking business over the summer and charged $7 for an hour walk. She walked a total of 57 dogs during June, July, and August. If Lauren walked the same amount of dogs each month, how much money did she earn in July? (PARCConline.org – evidence tables) 10 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Use the four operations with whole numbers to solve problems. Maryland College and Career-Ready Standards 4.OA.3 Solve multistep word problems posed with whole numbers and having wholenumber answers using the four operations, including problems in which remainders must be interpreted. Represent these problems using equations with a letter standing for the unknown quantity. Assess the reasonableness of answers using mental computation and estimation strategies including rounding. NOTE: This is the first time students are expected to interpret remainders based upon the context. All four operations will be addressed in Unit 5 – solving measurement problems, and the standard will be finalized at the end of the year. Instructional Strategies and Resource Support C. More often than not, division does not result in a simple whole number. In some division word problems, a leftover quantity … or, remainder … needs to be interpreted. Remainders may have several different effects on answers. Focus in Grade 4: Teaching with Curriculum Focal Points Interpreting remainders – pp. 22-23 It is useful to include, in instruction, story problems with remainders and explore the different ways that students handle these in context. The following examples illustrate various interpretations of remainders: You have 30 pieces of candy to share fairly with 7 children. How many pieces of candy will each child receive? Left over amount: 4 pieces of candy and 2 left over The rope is 25 feet long. How many 7-foot jump ropes can be made? Discarded amount: 3 jump ropes and 4 feet left over A ferry can hold 8 cars. How many trips will it have to make to carry 25 cars across the river? Pushed up to next whole number: 4 trips Six children are planning to share a bag of 50 pieces of bubble gum. About how many pieces will each child get? Rounded result: About 8 pieces of bubble gum for each child SMP 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. 6. Attend to precision. 7. Look for and make use of structure. Formative Assessments Students will need to write equations with a letter standing for the unknown quantity to represent these problems. Additionally, they need to be able to recognize that more than one equation may accurately represent a problem. 11 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Use place value understanding and properties of operations to perform multidigit arithmetic. Maryland College and CareerReady Standards 4.NBT.5 Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models. Instructional Strategies and Resource Support Formative Assessments Focus in Grade 4: Teaching with Curriculum Focal Points pp. 13-18 4.NBT.B.5a Teaching Student-Centered Mathematics – Grades 3-5 Expanded Lesson: Area Model for Multiplication, pp. 129-130 Strategies for Multiplication pp. 113-118 Students should use a variety of strategies to multiply numbers. Developing flexibility in breaking numbers apart allows students to have a stronger understanding of the importance of place value and the distributive property in multiplying multi-digit numbers. Children may use area models, base-10 blocks, compensation strategies, etc. to multiply whole numbers, then use words and diagrams to explain their thinking. Using a variety of strategies enables students to develop fluency with multiplication, as well as transferring their understanding to division. The standard algorithm for multiplication is an expectation in the 5th grade. The average Maryland blue crab measures 8 inches long. If you placed 153 crabs end to end in a line, how long would the line be? 4.NBT.B.5b Solve the following problem in 2 different ways. 63 x 47 NOTE: Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000. Students build on their understanding of multiplication from 3 rd grade. They move beyond multiplying a one-digit number by a multiple of 10 to multiplication of a onedigit number by a whole number of up to four digits and to multiply two two-digit numbers. Students benefit from building arrays/area models using base-ten blocks to multiply greater numbers. Examples: SMP 6 rows 4 x 632 6 x 10 = 60 20 rows 3. Construct viable arguments and critique the reasoning of others. 6. Attend to precision. 7. Look for and make use of structure. 4.NBT.B.5c Find the product of each. 13 per row 10 per row How are both of your strategies alike? 20 x 13 = 260 Can be broken apart in many ways including: 10 x 13 = 130 10 x 13 = 130 130 + 130 = 260 SMP Students use strategies and base explanations on properties of operations, the relationship between multiplication/division, and place value. (PARCConline.org – evidence tables) 4 x 623 What do you notice about the problems? What conclusions can you make? 4.NBT.B.5d At Camden Yards, the seats in section 68 are located by third base. There are 27 rows in this section. If each row has 14 seats, how many seats are there? Solve this problem in more than 1 way. 12 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Use place value understanding and properties of operations to perform multi-digit arithmetic. Maryland College and CareerReady Standards 4.NBT.5 Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models. Instructional Strategies and Resource Support Formative Assessments The distributive property over addition allows numbers to be decomposed into base-10 units, then have units be computed and combined. By decomposing the factors into like base-10 units and applying the distributive property, multi-digit computations are simplified to single-digit multiplications and products of numbers with multiples of 10, 100, and 1,000. Students can connect using an area model to thinking developed previously with base-10 block arrays. This problem can be seen as 8 rows of 549 decomposed into 8 x 500 + 8 x 40 + 8 x 9. Students will apply multiplication patterns when multiplying by multiples of 10. NOTE: Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000. SMP 3. Construct viable arguments and critique the reasoning of others. 6. Attend to precision. 7. Look for and make use of structure. Example: 36 x 94 = (30 + 6) x (90 + 4) = (30 + 6) x 90 + (30 + 6) x 4 = 30x90 + 6x90 + 30x4 + 6x4 = 2,700 + 540 + 120 + 24 = 3,384 13 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Use place value understanding and properties of operations to perform multi-digit arithmetic. Maryland College and CareerReady Standards 4.NBT.6 Find wholenumber quotients and remainders with up to fourdigit dividends and onedigit divisors, using strategies based on place value, the properties of operations, and/or the relationship between multiplication and division. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models. NOTE: Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000. SMP 3. Construct viable arguments and critique the reasoning of others. 6. Attend to precision. 7. Look for and make use of structure. 8. Look for and express regularity in repeated reasoning Instructional Strategies and Resource Support Focus in Grade 4: Teaching with Curriculum Focal Points pp. 22-23 Students begin to build on their understanding of basic division facts, using problems that do not “come out even.” This will help students develop an understanding of remainders. Students can use familiar models including base-10 blocks and pictures to solve non-basic fact division equations. Students strengthen understanding of how to use multiplication to solve division problems. They can think of division as an “unknown factor” problem. For example: 35 ÷ 8 = m Think 8 x m = 35. Students move towards thinking of the closest multiple of 8 that is under 35. (8 x 4 = 32) and then determine how much more is needed to get to 35. (8x4) + 3 = 35 Therefore, 35 ÷ 8 = 4 r 3. After students have had ample experience with “near facts” (quotient and divisor are both less than 10, but there is a remainder), then move to division problems with quotients more than 9. The processes then evolve into invented strategies for division. Students apply their understanding of multiplication patterns with multiples of 10. For example: 47 ÷ 3 Possible solution: I know that 3 x 10 = 30. 47 – 30 = 17. I know that 3 x 5 = 15. If I take 15 from 17, I’m left with 2. I have 10 groups of 3 and 5 groups of 3 OR (10 + 5) x 3 with 2 left over. My answer is 15 r 2. Teaching Student-Centered Mathematics pp. 121-122 Formative Assessments 4.NBT.B.6a Kim is making sandwich platters for a party. The table below shows the total number of each type of sandwich she made. She has small, medium, and large trays to hold the sandwiches. What combination of all three different-size trays can be used to hold all of the sandwiches that Kim made? 4.NBT.B.6b At the bakery, Michael is decorating cupcakes with mini-pumpkin candies. He has 46 pumpkins to place on 6 cupcakes. As he decorates, Michael places one candy at a time on each cupcake and continues in this way until all candies are used. 4.NBT.B.6c Solve 92 ÷ 4 in 2 different ways. Which way was most efficient for you? Why? SMP Students use strategies and base explanations on properties of operations, the relationship between multiplication/division, and place value. (PARCConline.org – evidence tables) 14 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Use place value understanding and properties of operations to perform multi-digit arithmetic. Maryland College and CareerReady Standards 4.NBT.6 Find wholenumber quotients and remainders with up to fourdigit dividends and onedigit divisors, using strategies based on place value, the properties of operations, and/or the relationship between multiplication and division. Illustrate and explain the calculation by using equations, rectangular arrays, and/or area models. NOTE: Grade 4 expectations in this domain are limited to whole numbers less than or equal to 1,000,000. SMP 3. Construct viable arguments and critique the reasoning of others. 6. Attend to precision. 7. Look for and make use of structure. 8. Look for and express regularity in repeated reasoning Instructional Strategies and Resource Support Formative Assessments Computing quotients of multi-digit numbers and one-digit divisors relies on the same understandings as for multiplication. For example, recognizing that 56 ÷7 is related to 560 ÷7 and 5600 ÷7. Students should also be able to reason that 5600 ÷ 7 means partitioning 56 hundred into 7 equal groups, so there are 8 hundreds in each group. Another general method for multi-digit division computation is decomposing the dividend into like base-10 units and finding the quotient unit-by unit. This requires an understanding of the distributive property. Progressions for the Common Core State Standards in Mathematics (draft, 2012) Students should remain flexible in their understanding of breaking numbers apart when dividing. Not all approaches will be the same, but solid place value understanding should be applied. Examples of solutions for 537 ÷ 8. There are 60 8’s in 537. 537 – 480 = 57 There are 7 8’s in 57. 57 – 56 = 1 60 + 7 = 67 8’s with 1 left 8 ) 537 - 400 137 80 57 56 1 8 x 50 8 x 10 67 8’s 8x 7 67 r 1 15 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days Solve problems involving measurement and conversion of measurements from a larger unit to a smaller unit. Maryland College and CareerReady Standards 4.MD.3 Apply the area and perimeter formulas for rectangles in realworld and mathematical problems. For example, find the width of a rectangular room given the area of the flooring and the length, by viewing the area formula as a multiplication equation with an unknown factor. NOTE: This standard provides the context of area and perimeter of rectangles to use for problem-solving. Students are first introduced to formulas in this unit and make sense of the formulas using their prior work with area and perimeter. SMP 1. Make sense of problems and persevere in solving them 2. Reason abstractly and quantitatively 8. Look for and express regularity in repeated reasoning Instructional Strategies and Resource Support Students consider perimeter and area of rectangles by building on previous 3rd grade understanding. Fourth graders, through constructing arrays and applying features of rectangles, reason to develop and understand the formula for the area of a rectangle as A = l x w. The formula is based on the understanding that a rectangle, whose sides have a width of “w” units and a length of “l” units, can be partitioned into w rows of unit squares with l squares in each row. The product l x w gives the number of unit squares in the rectangle. Students use the relationship between multiplication and division to solve problems in which the length of a missing side needs to be found. Given the area and one side, students can divide to find the missing side. Teachers should emphasize that it is not important to designate a specific number as the width in a rectangle because of the commutative property of multiplication. Examples of Area Problems: *Jacob’s desk is 32 inches by 18 inches. Ella’s desk is 24 inches x 24 inches. Whose desk is larger? What could we do to give both students the same amount of work space on their desks? *Determine how many square inches are in one square foot. *The area of a rectangle is 36 square centimeters. The length is 5 centimeters longer than the width. What is the perimeter of the rectangle? Additional resources – Measuring Area: Formative Assessments 4.MD.A.3a Sarah is painting a mural on her bedroom wall. She gets to choose which wall she would like to paint. The first wall is 17 feet by 8 feet. The second wall is 14 feet by 11 feet. Which wall has more space for the mural? Show your work. 4.MD.A.3b The area of Drew’s rectangular kitchen is 120 square feet. The width of the kitchen is 8 feet. What is its length? Include a labeled diagram of Drew’s kitchen. 4.MD.A.3c In Mia’s garden, she plants carrots in one section and all of the green vegetables in another section. The total area of Mia’s garden is 120 square feet. Use the diagram below to help you find the area of the carrot section. green vegetables carrots Teaching Student-Centered Mathematics Grades 3-5 pp. 261-264 Expanded lesson: Fixed Areas (Based on Activity 9.7) pp. 288-289 Focus in Grade 4: Teaching with Curriculum Focal Points pp. 60-67 16 Carroll County Public Schools Elementary Mathematics Instructional Guide (Grade 4) Unit 2: Multiplication and Division - 28 Days In Quarter 1, students will be expected to solve all equal groups situations and arrays/areas situations. Students will be expected to represent the highlighted problem situations with equations on assessments. 17