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* *Reflection: Lesson Planning
Getting Bigger and Smaller - Section 2: Teaching the Lesson

Second graders are still developmentally at a stage where concrete models and pictures help them to grasp mathematical concepts. Common Core standard 2.NBT.7 states that students should be able to add and subtract within 1000 using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

Too often students memorize number facts without understanding underlying concepts. In this lesson I wanted even the students who can read and write numbers in the hundreds to stop and build those numbers to solidify their understanding of the importance of place value. I find that letting students "play" with blocks and other manipulatives, even when they can perform the operation, strengthens their understanding of the concept being taught.

*Using Models to Solve Problems*

*Lesson Planning: Using Models to Solve Problems*

# Getting Bigger and Smaller

Lesson 7 of 18

## Objective: SWBAT extend their understanding of the base ten system using its properties to add, subtract and compare two and three digit numbers.

#### Warm Up

*10 min*

I create a grid on the board and place a digit 1 in the hundreds place, digit 3 in the tens place and digit 2 in the ones place, leaving a blank in the middle for students to add < > =, and then place a digit 2 in the hundreds place, a digit 6 in the tens place and a digit 8 in the ones place.

1 hundred 3 tens 2 ones ______________ 2 hundreds 6 tens 8 ones

(I have written the words so that students can think about what they know about base ten numbers (a Common Core requirement) and how the numbers are built.

I read the descriptions aloud. I ask students to write the numbers I am describing and add the greater than, less than or equal to sign in the middle. I remind them that the alligator likes to eat the larger number.

I ask for a student to come up and write the two numbers and the sign on the board. I ask for a thumbs up from students who figured out the two numbers.

(The child writes 132 < 268)

I write a second example on the board and repeat the process.

3 hundreds 4 tens 1 one _____ 4 hundreds 3 tens 5 ones

If students are still struggling I may work through several more examples.

I ask students to stretch and then come to the rug for the next part of the lesson.

*expand content*

#### Teaching the Lesson

*30 min*

Students have been hearing and using the terms digit, ones, tens and hundreds. We have not yet talked about expanded notation for numbers.

For most students, expanded notation was introduced in 1st grade where students learned that 11 is made up of 1 ten and 1 one, and twenty is made up of 2 tens. Today we will review this concept and expand it to include hundreds.

I review expanded notation with students using base ten blocks, ask them to practice with me, and then they will have a chance to practice on their own. We will be able to add and subtract the blocks and compare our numbers as we practice.

I write the number 135 on the board. I ask a student which digit is in the ones place? I ask them to take that many ones out of the box. Next I ask which digit is in the ten's place and have a student take the right number of tens. I repeat this with the hundreds.

I write:

*1 hundred, 3 tens and 5 ones* in words next to the number and ask students if the two are equal? How do they know that the two numbers are equal? (I am looking for students to be able to identify that in the numeral 135 the one represents 1 hundred, the 3 represents 3 tens and the 5 represents 5 ones and that is the same as the words.) I help students to verbalize their understanding of how the words represent the digits in a number.

I repeat the process with the number 269.

Now I write:

*1 hundred, 5 tens and 4 ones* on the board. I ask a student to take the correct number of blocks. We check it together. I ask a student to come up and write the number on the board next to the words.

I repeat this with the number 248.

Now I tell students that today they will be working in 3 groups, with numbers in the hundreds. Some will be building numbers and comparing them with the alligator (greater than less than mouths) and some will be adding numbers by building 2 numbers and then putting them together to create a new quantity.

The students who can build numbers independently will work on adding two numbers. They will build both numbers reading the expanded notation form, building the numbers the words represent, and then combining the blocks to get an answer. This may allow them to trade 10 bundles of 10 for a 100 block. (MP1-Students are making sense of problems by using the models and then persevering in solving them.)

The students who are still working on reading the expanded notation will build two numbers in the hundreds, and then compare them using the greater than/less than alligators.

Students will work for about 15 minutes of practice time.

#### Resources

*expand content*

#### Closing

*15 min*

Students return to the rug for a closing. This time I put two numbers on the board. I ask a student to show me which is greater using the <> symbol.

Next I ask if anyone could come up and change the first number to 10 more. We discuss which digit should be changed to show a change of tens. I ask a student to do the same with the second number. Would the <> symbol change when I add 10 more to both numbers? Why or why not? Could it change if I added 10 more to just one number? When might that happen?

As we close I ask each student what 10 more than or 10 less than a number is. As they answer, they are free to line up for our move to specials. This is a quick check on their grasp of 10 more or 10 less.

*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