##
* *Reflection: Continuous Assessment
Double-Digit Subtraction - We Can Do It - Section 3: Ongoing Assessment

I have given students a wide variety of strategies this year to solve double-digit subtraction problems. I know that I could give them just one and they could all memorize the steps and complete the problems. However, my goal is that they understand the process and complete problems in the best way for them. Students learn differently. By providing a wide variety of strategies, I am encouraging students to meet the Common Core goal of being able to explain why addition and subtraction strategies work based on place value understanding. I am also teaching students to choose the appropriate tool (MP5) for solving a problem that they are faced with.

*Why So Many Strategies*

*Continuous Assessment: Why So Many Strategies*

# Double-Digit Subtraction - We Can Do It

Lesson 6 of 16

## Objective: SWBAT use manipulatives and drawings to solve double-digit subtraction problems.

## Big Idea: It takes practice to complete double-digit subtraction problems so today's lesson allows for that practice in several subtraction centers.

*70 minutes*

#### Warm Up

*10 min*

I begin today with a subtraction facts practice page. The page has 25 problems up to 20 - 10 (all subtraction) to complete as quickly as possible. I create the page at MathFactCafe.com where I can put in the parameters for my subtraction page. I give students 2 minutes to complete as many of the problems as we can and then we correct the problems together so that students get immediate feedback regarding their fluency.

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#### Subtraction Centers

*50 min*

Today students will visit several subtraction centers. At each center they will be able to practice subtraction. I start by explaining each center to the students. I have a series of problems for Centers 2 and 3 for children to use when building the numbers. The problems are on large sheets and posted for all students to see. Each center encourages students to makes sense of the problems and persevere in solving them (MP1).

Center 1: Subtraction fact practice on the iPad. Students have the option of using several subtraction fact practice programs on the iPad to increase their fluency with subtraction facts. They use Math Bingo, Flash Card Math, and other programs that allow for immediate feedback and let students know if they are correct or incorrect.

Center 2: Ten Frames Subtraction: Students start by building the larger number with filled-in tens frames for the ten's digit and blank frames that they fill themselves with chips for the ones. Now they decide if they can subtract the necessary ones by taking away chips. If they can not, they turn one of the filled frames into a frame of chips (regroup) so that they now have enough ones.

Center 3: Subtraction Using Place Value Houses. Students build the larger number in the upstairs of the house and the number they are subtracting in the downstairs of the house. They subtract by matching the minuend blocks with the subtrahend blocks and removing them from the house. They regroup when necessary to match tens with tens and ones with ones.

Center 4: Paper and Pencil Double-Digit Subtraction: Students may draw the base 10 blocks or tens frames to solve these regrouping problems. Students need to choose the tools that are appropriate for solving the problem(MP5).

Once I have explained all the centers, I break students into groups, based on understanding of double-digit subtraction. I want homogeneous groupings so that students who are more confident can begin with the paper and pencil subtraction center. I get each group centered for each round of centers and then I work mostly with the group visiting Center 3. This is the center that takes the most support for students to do.

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#### Ongoing Assessment

*10 min*

I ask students to return to their seats. I give students 2 double-digit subtraction problems to complete. One of the problems requires regrouping and the other does not. The problems are 71 - 46 =, and 65 - 32 = . I tell them they may use any of the strategies that they have used today, or previously, to solve the problems (MP1).

I collect these problems to assess student progress with double-digit subtraction.

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- UNIT 1: What and Where is Math?
- UNIT 2: Adding and Subtracting the Basics
- UNIT 3: Sensible Numbers
- UNIT 4: Sensible Numbers
- UNIT 5: Everything In Its Place
- UNIT 6: Everything in Its Place
- UNIT 7: Place Value
- UNIT 8: Numbers Have Patterns
- UNIT 9: Fractions
- UNIT 10: Money
- UNIT 11: The Numbers Are Getting Bigger
- UNIT 12: More Complex Numbers and Operations
- UNIT 13: Area, Perimeter and More Measurement
- UNIT 14: Length
- UNIT 15: Geometry
- UNIT 16: Getting Ready to Multiply
- UNIT 17: Getting Better at Addition and Subtraction
- UNIT 18: Strategies That Work

- LESSON 1: My Special Strategies
- LESSON 2: Division Strategies
- LESSON 3: Estimation as a Strategy for Checking Work
- LESSON 4: Using Math at Work
- LESSON 5: Measurement Strategies
- LESSON 6: Double-Digit Subtraction - We Can Do It
- LESSON 7: Where On The Line?
- LESSON 8: Stop, Look and Check
- LESSON 9: Stop, Look and Check (Part 2)
- LESSON 10: Attributes of Groups
- LESSON 11: Relative Size
- LESSON 12: Counting Coins Again
- LESSON 13: Another Visit to Double-Digit Work
- LESSON 14: Visiting the Olympics
- LESSON 15: Creating Math Games
- LESSON 16: Playing Our Own Games