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Division Unit: Writing A Number Sentence

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Division Unit: Writing A Number Sentence

Heather Breaux
3rd. Grade
Division Unit
Lesson 4: Writing a Number Sentence
Approximate Time: 60 minutes

Berks County Standards:
1. 2.5.3 Mathematical Problem Solving and Communication- B. Determine when sufficient information is present to solve a problem and explain how to solve a problem.
2. 2.1.3 Numbers, Number Systems and Number Relationships- C. Represent equivalent forms of the same number through the use of concrete objects, drawings, word names and symbols.
3. 2.1.3 Numbers, Number Systems and Number Relationships- L. Demonstrate knowledge of basic facts in four basic operations.
4. 2.2.3 Computation and Estimation- D. Demonstrate concept of division as repeated subtraction and as sharing.

NCTM Standards:
1. Number and Operations
2. Algebra
6. Problem Solving
7. Reasoning and Proof
8. Communication
10. Representation

Behavioral Objectives: Upon completion of this lesson, students will be able to….
1. Solve problems using the strategy writing a number sentence
2. Determine whether multiplication or division is used in each problem given

Materials/Technology Needs: Students textbooks; WS “Reteach 12.5” RW66; WS “Practice 12.5” PW66; “Multiplication” worksheet for homework; dry erase boards and markers.

Anticipatory Set: “Today we all need to put our thinking caps on because we’re going to be reading fun word problems and trying to figure out whether to use multiplication or division. In order to do this, let’s get our math minds working and do some practice problems!” Write “Quick Review” problems from p. 250 on board and call on volunteers to answer the questions.
Problems: 8x4= ; 30=6x?; 10x5= ; 18= ?x6; 27=9x?

1. Introduce that today’s task for everyone is to identify what kind of process (multiplication or division) is being used in today’s word problems and then to write the number sentence that is being used for us to solve. Identify the 4 steps to finding the number sentence in a problem by writing the following steps on the board and having students read each step. Have the class echo read after the student has finished reading each step aloud.
Step 1: What operation do you need to use to solve the problem? How do you know?
Step 2: Write the sign of the operation you choose, an equal sign, and boxes where the number’s go.
Step 3: Think and discuss what should go in each box.
Step 4: Fill in the numbers and solve.
2. Have students turn to p. 250 in their textbooks to read the problem about animal trading cards. Go through the steps listed above to identify and solve the number sentence.
A. Begin by asking the following questions:
4. “What does the problem ask you to find? (How many pages are needed)
5. What information will be used, meaning what’s important from the problem? (36 cards, 9 cards on each page).
6. Any information that won’t be used? (no)
B. Ask them what strategy can be used? Remind them that multiplication is used when you are joining groups together of equal size and division is used when we are separating groups of equal size. Division can also be used when you know the total.
C. When students determine division is to be used, write the number sentence with boxes for where the numbers are to go. Determine where each number goes in the number sentence.
D. Solve for the answer (4). Ask students how they can check their work (by using multiplication because it’s the inverse operation of division). Write inverse operation on the board to trigger their memory of yesterday’s lesson on inverse operations and fact families. Ask students to come up with the multiplication problem that can be used to check our problem. Have them whisper it to a partner before we go over it as a class.
3. Pass out WS “Reteach 12.5”. Call on students to read the top of the page as a refresher as to when to use multiplication and division to solve word problems. Solve problems 1-4 together as a class by using the 4 steps. Leave the steps on the board for the students to refer to while solving.
4. Hand out WS “Practice 12.5” to the class. Students may work in pairs to complete problems 1-4, while I roam the room to assist them. Problems 5-22 must be completed individually once 1-4 are solved in pairs.
5. Pass out WS “Multiplication” for homework.

Accommodations: I will seat Jessica at the front of the room so that she can see all problems on the board, as well as provide her with enlarged worksheets to work with at her desk and for homework.

Closure: Put the following sentences up on the overhead and have the students fill in the blanks by writing their answers on dry erase boards at their seats.
1. ________ is used when you are joining groups of equal size.
2. ________ is used when you know the total.
3. Multiplication and division are _______ operations.
4. ________ is used when you are separating a total into groups of equal size.

Key Questions:
1. “How do we know when to use multiplication in a word problem?”
2. “How do we know when to use division in a word problem?”
3. “Who can list the 4 steps to identifying a number sentence and solving a word problem?”

Evaluation: For my formative assessment, I will judge my students knowledge of identifying number sentences by how well they can answer by questions for problems 1-4 on “Reteach 12.5”. I will be using their homework assignment “Multiplication” and the Mixed Review problems 5-22 from “Practice 12.5” for my summative assessment.

Assignment: WS “Challenge 12.5” CW66.
Resources Used:
1. (2004). Harcourt Math Teacher Edition: Third Grade. Vol. 2.) Harcourt, Inc.
2. edHelper at url

Frank D'Angelo, who submitted these articles, writes: [This] is an excellent unit submitted by a student in my Elementary Mathematics Methods Course.

Lesson by Frank D'Angelo

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