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# Counting with Tens and Hundreds

Lesson 17 of 18

## Objective: SWBAT add or subtract 10 from any 2 digit number and use a model to add or subtract 100 from any 3 digit number

#### Warm Up

*10 min*

To support the Common Core standard of being able to add and subtract 10 from a number mentally, we begin by practicing *partners of ten* mental math. I call out a p*artner of ten* fact and students respond by holding up the number of fingers to make 10. I call out 6, they hold up 4. I call out 9, they hold up 1.

Next, to recall prior learning of equal number sentences, I put the number sentence 16 + 4 = ___ + 8 on the board. Students find the missing number. I ask students to identify the partners of ten that they see in the equations.

I repeat this with another sentence. 12 + ____ = 9 + 11. We comment on the partner of ten found within the sentence.

I tell students that today we will begin on the rug. I ask them to count back from 20 as they walk to the rug.

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#### Teaching the Lesson

*15 min*

To meet the diverse entrance points of the learners in my classroom, I create several different IN/OUT tables for students to work on independently. I want all students to be challenged, but not overwhelmed.

One group will work with adding and subtracting with 5s and 10s in the IN/OUT boxes. Another group will extend their understanding by adding and subtracting with money (dimes and dollars) in their IN/OUT boxes.

Each group will also have a chance to work with a cardboard IN/OUT machine and to explore how the numbers are changing and to see if they can apply that change to different numbers.

The independent practice will allow students to explore the adding and subtracting of 10 and 100 from a number. I want students to begin to internalize this process so that it becomes automatic and rather than having to count, they can realize that by using the idea of place value, they can change just the tens or hundreds place up or down.

*expand content*

#### Independent Practice

*20 min*

To meet the diverse entrance points of the learners in my classroom, I create several different IN/OUT tables for students to work on independently. I want all students to be challenged, but not overwhelmed.

One group will work with adding and subtracting with 5s and 10s in the IN/OUT boxes. Another group will extend their understanding by adding and subtracting with money (dimes and dollars) in their IN/OUT boxes.

Each group will also have a chance to work with a cardboard IN/OUT machine and to explore how the numbers are changing and to see if they can apply that change to different numbers.

The independent practice will allow students to explore the adding and subtracting of 10 and 100 from a number. I want students to begin to internalize this process so that it becomes automatic and rather than having to count, they can realize that by using the idea of place value, they can change just the tens or hundreds place up or down.

*expand content*

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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: Let Me Count The Ways to Get An Answer
- LESSON 2: Who Makes Mistakes
- LESSON 3: Counting Up to Solve Problems
- LESSON 4: Counting Backwards Works Too
- LESSON 5: Counting Bugs
- LESSON 6: Taking Apart the Problem
- LESSON 7: Getting Bigger and Smaller
- LESSON 8: Double It
- LESSON 9: Doubles Plus or Minus One
- LESSON 10: Evens and Odds
- LESSON 11: Plus Ten Minus Ten
- LESSON 12: From Tens to Nines
- LESSON 13: Equal Amounts
- LESSON 14: Understanding Subtraction
- LESSON 15: Skip Counting with 5s, 10s and 100s
- LESSON 16: Balancing Equations and Counting Backwards
- LESSON 17: Counting with Tens and Hundreds
- LESSON 18: Assessment