Add Your Way
10 min
Narrative
The purpose of this Number Talk is to elicit the strategies and understandings students have for adding three-digit numbers. These understandings help students develop fluency and will be helpful later in this lesson when students use strategies based on place value and properties of operations to add within 1,000.
Launch
- Display one expression.
- “Give me a signal when you have an answer and can explain how you got it.”
- 1 minute: quiet think time
Teacher Instructions
- Record answers and strategies.
- Keep expressions and work displayed.
- Repeat with each expression.
Student Task
Find the value of each expression mentally.
- 100+30+4
- 9+400+50
- 40+600+12
- 500+17+130
Solution Steps (4)
- 1100 + 30 + 4→134 (combine hundreds, tens, ones directly)
- 29 + 400 + 50→459 (rearrange to 400 + 50 + 9)
- 340 + 600 + 12→652 (decompose 12 = 10 + 2, so 600 + 40 + 10 + 2 = 600 + 50 + 2)
- 4500 + 17 + 130→647 (500 + 100 = 600, 30 + 10 = 40, 7 ones → 647)
Sample Response
- 134: I just thought about combining the hundreds, tens, and ones.
- 459: I saw that there were hundreds, tens, and ones, but they were just mixed up.
- 652: I saw that there were hundreds. Then I broke the 12 into a 10 and a 2. Then there were 6 hundreds, 5 tens, and 2 ones.
- 647: I saw there were only 7 ones, but there were some tens in different places. I added up the tens from 17 and 130, which made 4 tens. Then I added up the hundreds from 500 and 130, which made 6 hundreds. So, there were 6 hundreds, 4 tens, and 7 ones.
Activity Synthesis (Teacher Notes)
- “How did you use place value to find the value of each sum?” (I added hundreds to hundreds and tens to tens.)
- Consider asking:
- “Who can restate _______ 's reasoning in a different way?”
- “Did anyone have the same strategy but would explain it differently?”
- “Did anyone approach the problem in a different way?”
- “Does anyone want to add on to____’s strategy?”
Standards
Building On
- 2.NBT.7·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; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
- 2.NBT.B.7·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; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Addressing
- 3.NBT.2·Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
- 3.NBT.A.2·Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
25 min
10 min
Knowledge Components
All skills for this lesson
Role Legend
Target
Essential
Supporting
Foundational
All lesson KCs
2 skills
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Add Your Way
10 min
Narrative
The purpose of this Number Talk is to elicit the strategies and understandings students have for adding three-digit numbers. These understandings help students develop fluency and will be helpful later in this lesson when students use strategies based on place value and properties of operations to add within 1,000.
Launch
- Display one expression.
- “Give me a signal when you have an answer and can explain how you got it.”
- 1 minute: quiet think time
Teacher Instructions
- Record answers and strategies.
- Keep expressions and work displayed.
- Repeat with each expression.
Student Task
Find the value of each expression mentally.
- 100+30+4
- 9+400+50
- 40+600+12
- 500+17+130
Solution Steps (4)
- 1100 + 30 + 4→134 (combine hundreds, tens, ones directly)
- 29 + 400 + 50→459 (rearrange to 400 + 50 + 9)
- 340 + 600 + 12→652 (decompose 12 = 10 + 2, so 600 + 40 + 10 + 2 = 600 + 50 + 2)
- 4500 + 17 + 130→647 (500 + 100 = 600, 30 + 10 = 40, 7 ones → 647)
Sample Response
- 134: I just thought about combining the hundreds, tens, and ones.
- 459: I saw that there were hundreds, tens, and ones, but they were just mixed up.
- 652: I saw that there were hundreds. Then I broke the 12 into a 10 and a 2. Then there were 6 hundreds, 5 tens, and 2 ones.
- 647: I saw there were only 7 ones, but there were some tens in different places. I added up the tens from 17 and 130, which made 4 tens. Then I added up the hundreds from 500 and 130, which made 6 hundreds. So, there were 6 hundreds, 4 tens, and 7 ones.
Activity Synthesis (Teacher Notes)
- “How did you use place value to find the value of each sum?” (I added hundreds to hundreds and tens to tens.)
- Consider asking:
- “Who can restate _______ 's reasoning in a different way?”
- “Did anyone have the same strategy but would explain it differently?”
- “Did anyone approach the problem in a different way?”
- “Does anyone want to add on to____’s strategy?”
Standards
Building On
- 2.NBT.7·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; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
- 2.NBT.B.7·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; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Addressing
- 3.NBT.2·Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
- 3.NBT.A.2·Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.