 Author:
 DAWNE COKER
 Subject:
 Mathematics
 Material Type:
 Activity/Lab, Lesson, Lesson Plan
 Level:
 Lower Primary
 Tags:
 License:
 Creative Commons Attribution
 Language:
 English
 Media Formats:
 Downloadable docs
Education Standards
T4T Adding 3Digit Numbers within 1000
Overview
This resource is from Tools4NCTeachers. In this lesson, students develop strategies for adding 3digit numbers, with a focus on adding in chunks. Students build this strategy of adding in chunks by mentally adding 10 and 100 to numbers, and adding on the number line.
Remix this lesson to include extension activities such as math stations.
Here is a sample from this lesson. Click to download the entire, fullyformatted lesson and support materials.
Adding 3 Digit Numbers Within 1000
In this lesson, students explore adding 3 digit numbers using different strategies. 
NC Mathematics Standard(s):
NC2.NBT.7 Add and subtract, within 1000, relating the strategy to a written method, using:
• Concrete models or drawings
• Strategies based on place value
• Properties of operations
• Relationship between addition and subtraction
Additional/Supporting Standards:
NC.2.NBT.6 Add up to three twodigit numbers using strategies based on place value and properties of operations.
NC.2.NBT.8 Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.
Standards for Mathematical Practice:
1. Make sense of problems and persevere in solving them
2. Reason abstractly and quantitatively
3. Construct viable arguments and critique the reasoning of others
4. Model with mathematics
6. Attend to precision
7. Look for and make use of structure
Student Outcomes:
 I can add within 1,000.
 I can use models and drawings to demonstrate my understanding.
 I can compose and decompose numbers by hundreds, tens and ones in order to solve a problem.
 I can explain my strategies to my partner.
 I can explain my work using pictures, words, or numbers.
Math Language:
What words or phrases do I expect students to talk about during this lesson?
I know 5+5=10, then I know 50+50=100 and 500+500=1000
I added hundreds to get _____; I added tens to get _____; I added ones to get ______.
My strategy to solve this problem was ______.
I used ________ strategy.
I expanded my numbers to _______.
Materials:
 Manipulatives such as, but not limited to: base ten blocks, hundred boards
 Whiteboards and dry erase markers
 Math journals
 Anchor charts showing different strategies of two digit addition displayed
Advance Preparation:
 Students have participated in Mental Math or Number Talks for many weeks with problems that begin with: What is 10 more than?: 80, 110, 220, etc.
Advancing to: What is 10 more than?: 95, 148, 365, etc.
Then moving to: What is 100 more than?: 500, 800, etc.
Advancing to: What is 100 more than?: 314, 580, 723, etc.
 Students are familiar with different strategies to solve 2 digit addition
Launch:
Who’s Right? (510 minutes)
 Present this problem to the students:
Ed and Tom were showing 345 with their materials.
Ed showed 345 with 3 hundreds, 4 tens and 5 ones.
Tom showed 345 with 3 hundreds, 3 tens and 15 ones.
 Allow students to justify their thinking about who was right.
 Is there another way to show 345?
 Could you use an open number line to show 345?
Teacher Note:
 If a group determines either Tom or Ed were correct, ask them to prove it to the class.
 When a group says, “They are both right,” allow them to justify their answer to the class.
Explore: (20 minutes)
Allow students to work with partners to solve the following problem:
There are 251 girls and 328 boys in an elementary school. How could you show the total number of students in this school?
 Teacher will monitor the students’ work; asking appropriate questions.
 How did you begin to think about this problem?
 What will be your next step?
 Tell me about the strategy you chose to solve the problem?
 What is another way you could solve the problem?
 What would happen if___?
 When partners have one strategy, ask them to decide on a second strategy to check their work.
 Allow students to join another group to check their answers.
 Create a list of the different strategies your group used to solve the problem.
Discuss: Prove it (20 minutes)
Allow students to show different strategies on how they solved the problems and discuss using talk moves.
Possible Strategies  Possible Discussion Prompts 
Expanded form Base ten blocks Open Number line Landmark numbers Create easier or known sums  How is ____ strategy similar to ____ strategy? How is ____ strategy different from ____ strategy? Why did you decompose your number in that way? Which strategy is most efficient? Explain why you think that.

Allow students to ask questions for clarification
Additional Activities (if needed)
Solve the following problem using 2 different strategies:
If a teacher has 457 pencils and 289 pens, how many writing instruments do they have in all?
 Can you show two strategies to solve?
 Allow students to explain their thinking to their partner, teacher or another group.
Evaluation of Student Understanding
Informal Evaluation:
 Teacher will make note of partners that did not solve the problem correctly and reasons why.
 Teacher will ask questions to groups to explain their thinking.
Formal Evaluation/Exit Ticket:
 Explain what strategy you would use to solve this problem:
370+298=
 The teacher will evaluate if additional instruction is needed.
Meeting the Needs of the Range of Learners
Intervention:
 Students who did not have the correct answer will be grouped for small group intervention to use manipulatives
Extension:
 Have students create their own addition problem and allow a partner to solve.
 Give solutions that are incorrect. (Error analysis) Can the student find the mistake?
Possible Misconceptions/Suggestions:
Possible Misconceptions  Suggestions 
Students may not have a clear understanding of place value.
 Continue to build numbers and use expanded notation to practice the place values. 
Special Notes:
 Place value is an important understanding within this math strand. Students will need a lot of practice with numerous numbers.
Possible Solutions:
Students begin with easier numbers (ones) and build up to