Primary Type: Lesson Plan
Status: Published
This is a resource from CPALMS (www.cpalms.org) where all educators go for bright ideas!
Resource ID#: 72942
Let’s Find the Missing Addend
This lesson will move students thinking that numbers can be moved around to solve a subtraction sentence. The students will use a related addition
fact and a part, part, whole mat to help them find the missing addend in a subtraction equation.
Subject(s): Mathematics
Grade Level(s): 1
Intended Audience: Educators
Suggested Technology: Document Camera,
Overhead Projector
Instructional Time: 1 Hour(s)
Resource supports reading in content area: Yes
Freely Available: Yes
Keywords: missing addends, subtraction
Resource Collection: FCR-STEMLearn Mathematics General
ATTACHMENTS
Missing addend worksheet (2).pdf
paper counters 2nd attempt.pdf
Part part whole mat 4.pdf
Recording of student understanding of missing addends.pdf
Situational Story Problem.pdf
Strips of subtraction sentences.pdf
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
Students will identify the missing addend in 4 different subtraction sentences using the Part, Part, Whole strategy.
Write and or illustrate 4 subtraction sentences with the missing addend.
Prior Knowledge: What prior knowledge should students have for this lesson?
Students should know how to count accurately to 20.
Students should be able to represent addition and subtraction using objects and numbers 0-20.
Guiding Questions: What are the guiding questions for this lesson?
How can we check to see what is 10-2=?
How do you know this answer is true?
What strategies did you use to help you find your answer? Why?
How did you use the part part whole mat to help you find the missing addend?
What addition equation will help you find the missing addend for this subtraction equation?
Show how you moved the counters to find the missing addend.
Teaching Phase: How will the teacher present the concept or skill to students?
1. Introduce Missing Addend Concept by using the following Hook: Prior to the activity place 6 cars around the room hidden, but that can be easily found.
2. Introduce the situation. The teacher may write the situation problem on the board or project the situational problem using an LCD projector and/or document
page 1 of 4 camera.
I had 8 toy cars at my desk, but now I only have 2 cars. I need to find out how many cars are missing.
3. Write the subtraction sentence on the board 8-2=?.
4. Think aloud:
Now I have 2 toy cars and some toy cars are missing. I will write 2 plus some cars = the 8 cars that I know I had to start with, 2+? =8
5. Ask students why they think you wrote a question mark instead of a number in the equation. Students should respond with that is the amount we do not know.
6. Invite six students to locate the cars. Each student will take a turn to locate one car. The other students are sitting in their seats. They may tell their classmates
using soft voices if they see a car. As the cars are found write the numbers of cars found on the board.
Ask students: How can we check if we found all the cars?
Ask students: What information in this situation do we know that will help us find the missing (amount) addend?
7. Set up the problem on a part part whole mat or project the bottom part of the situational story page. (See link above.)
Ask students: If I had 2 cars and we had to find some more to get to 8, how would I could I draw this on my mat?
8. The teacher will write students response in the Part, Part, and Whole Box on the board.
9. Explain: The missing number is my missing addend. Addends are two parts of a whole.
Guided Practice: What activities or exercises will the students complete with teacher guidance?
After you have modeled how to use the Part, Part, Whole Mat, tell students that we are going to solve for some missing counters.
Prepare ahead:
Count 15 counters into 18 Zip-lock storage bags. (If you do not have counters, you can use these paper counters.)
Give students the counters and a part, part, whole mat.
Tell students:
1. Tell students that we are going to use the part, part, whole mat to practice finding the missing addend in a subtraction sentence. And, that we are going to use
addition to help us find the missing addend.
2. Say: Let's find out what is 15-4?
3. Ask students: What addition sentence can we use to help us? Student response: 4+?=15
4. Tell students that we need to show this on our mat.
ask: What is the first thing we do? Students will say first we put 15 of our counters on the whole part of our mat.
Next, They will say that we need to take 4 counters from the whole and then place them on one part.
Then, they will say that the missing addend is 11.
You say: So, if you add 4 and 11 you will have 15 counters. If this is true, what is our missing addend? Students will say 11.
5. Ask: If 4+11=15, then what is 15-4? Student response is 11.
6. Tell students: Let's try another one. Let's say the problem is 12 - 5 = ?. What addition sentence could help us find the missing addend?
Student response is 5+?=12.
7. Tell the students to use their counters and the mat to solve the addition sentence.
8. Ask students: What is the missing addend? Student response is 7.
9. Say: If 5+7+12, then what does 12-5 equal? Student response is 7.
10. Move on to independent practice.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
After completing the Guided Practice:
Explain to students they will solve 2 subtraction equations by using the related addition sentence. Give each student the Missing Addend Worksheet.
Say: "You will now work with a partner to solve two subtraction sentences by find the missing addend in the related addition sentence."
Precut the subtraction sentences apart from the Strips of Subtraction Sentences sheet.
Give each student one problem from the sheet.
Students will work with their partner and write each subtraction sentences on their recording sheet.
Then they will write an addition sentence with the missing addend on their recording sheet using the numbers from the subtraction sentence. The students will
work with their partner to use the part, part, whole mats to find the missing addend.
Students will justify their answer to their partner by explaining how the addition sentence helped them solve the subtraction sentence.
Partners will present one subtraction sentence on the board.
At the end of partner work, give each student one more more problem from the strip of paper and a sheet of the paper counters. This problem will be glued into
their math journals and will be used for summative assessment.
Say: You will do this last problem on your own. Glue the problem to the top of your journal page. Write the related addition fact that will help
you find the missing addend. Draw a part, part, whole mat on your page and glue your counters on the mat to show the missing addend. When
you finish, write how you found the missing addend in the equation.
The teacher will collect the journals to assess each student's progress. Students are ready to move on if they could find the missing addend and explain how the
addition equation helped them solve the subtraction equation. Students who could not explain will need extra practice using this strategy.
Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
To bring closure to the lesson, the teacher will invite students to become reporters.
They will work with partners to write about a missing addend.
Example: I had ten counters and my partner took some. I had to find out how many he took. (The person who took counters must not share the amount he took
until the other person solved for the missing addend. Students will draw then explain how they got their answer.)
Each student will be given the opportunity to report on how his partner solved for the missing addend.
The teacher will listen to the student explanations and clarify any misconceptions by restating what students have said and asking questions about what steps the
student used to find the missing addend.
Summative Assessment
The teacher will give each student one more problem from the problem sheet used in independent practice and the paper counters. The students will glue this
problem into their math journals and solve it independently. The students will write the related addition sentence, draw a part, part, whole mat, and glue the counters
on the mat to show the missing addend. The teacher will collect the journals to assess each student's understanding. To be ready to move on, students will record the
page 2 of 4 correct related addition fact, find the correct missing addend, and be able to explain how the addition sentence and the part, part, whole mat helped them find the
addend.
Formative Assessment
Prior to lesson:
Review with students how to represent numbers of objects with written numbers. Draw objects of two given numbers. For example, draw 2 soccer balls, and then
draw 5 soccer balls. Ask students:Are the objects are one whole group? If so, why? If not, why? Then ask: How can we make a whole group of
soccer balls?
Draw a new picture to represent the whole group. The teacher will draw a part, part whole box on the board. Ask students to help you complete the box using the
numbers 2 and 5.
Ask students: What are the parts and what whole do they make?
1. After passing out counters, explain to students they will make the numbers 3 and 4. (Use Part, Part Whole Mat) a) Observe students creating and identifying the two
different addends using counters. Walk around the room and ask: b) What two parts do you see? 2) Tell: Put the two parts together. *Ask: What whole number did
you make? Students should be able to say 7. a) Observe students using counters by putting the two separate parts (addends) together. * Make a note of who might
have trouble with this activity. 3) During the independent activity: Students will demonstrate their understanding of finding the missing addend when writing an
addition sentence with the missing addend. The student will write their matching subtraction sentence in Math Journals. *See attachment in uploaded files.
Feedback to Students
For feedback, ask interview questions. Tell students you are a reporter and would like to interview them about their missing addends.
Walk around the room and ask individual students if they found their missing addends.
Ask Interview Questions:
"Have you found your missing addends"? "How did you find your missing addend?"
Ask students to give you directions on how to solve their addition sentence. Stop them if they missed a step. Repeat back to them what they just said.
ACCOMMODATIONS & RECOMMENDATIONS
Accommodations:
Give students an Individual Check List of what to do.
Give student a partner to work with.
Give extended time to complete missing addend worksheet.
Pull students in small group that need extra practice with the strategy.
Extensions:
Students will create a story about their missing addend. Give students a format to follow for the writing. Example: I have 7 blue crayons. Robert has some more blue
crayons. Altogether we have 13 crayons. How many crayons did Robert have?
I have______________. (friends name) has some more________________. Altogether we have________________________________________. How many
_____________________did (friends name)_____________have? ______. (friends name) has some more________________. Altogether we
have________________________________________. How many _____________________did (friends name)_____________have?
Suggested Technology: Document Camera, Overhead Projector
Special Materials Needed:
Real objects for teacher demonstration, for example toy cars 15
15 Counters per student (If you do not have access to counters, you can use these paper cut outs.)
Part, Part and Whole work mats - 1 per student (attached to the uploaded files)
Zip lock storage bags to hold counters - 1 per student (Helpful in preventing spills, also great for reusing and storing. )
2 sheets of the page strips of Subtraction sentences. (Directions are on the sheet.)
Students' Math Journals
paper coins for the summative assessment - 1 sheet per student
Missing addend worksheet (attached to the uploaded files)
Teacher Recording check list for understanding (attached to the uploaded files)
Further Recommendations:
Have the subtraction strips sheet cut apart before class begins.
Hide the 6 toy cars before students enter the room.
Additional Information/Instructions
By Author/Submitter
This lesson addresses the Mathematical Practice Standards: MAFS.K12.MP.4.1 Make sense of the problems and persevere in solving them.
The students will use this strategy as they answer questions like:
What do we already know about parts of whole numbers that might help us?
What looks familiar in the problem?
page 3 of 4 What is different?
How can we check to see if we found the correct missing addend?
SOURCE AND ACCESS INFORMATION
Contributed by: Patricia Weber
Name of Author/Source: Patricia Weber
District/Organization of Contributor(s): Miami-Dade
Is this Resource freely Available? Yes
Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
MAFS.1.OA.2.4:
Description
Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that
makes 10 when added to 8.
page 4 of 4