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Missing Addend Task Analysis
Grades K-2
Standard. Find the missing element (addend…) in addition and subtraction number sentences
for sums through 18 and minuends through 9.
This lesson is designed to move students from using concrete objects to explore the concept of
missing addend, to a pictorial representation of the concept, and then to the abstract solution.
Lesson Objective: Students will solve to find the missing addend in addition number sentences
for sums through 10.

Subobjective 1: TSW use concrete objects to demonstrate the concept of missing addend or
“How many more is needed?”.
o Input – Remember in addition sentences like 4+ 3 = 7, we call the numbers that we add
together the addends (4, 3) and the answer we get the sum (7). Today we will use cubes
to figure out how many more need to be added to a given number to find a specific sum.
When we are finished today, you will be able to solve problems like this: If I have 2
cubes, but need 5 total, how many more do I need to add? What is the missing addend?
o Modeling – Let me show you how to solve this problem.
Step 1: Place known number of objects on mat. Place 2 yellow cubes on mat.
Step 2: Write the total needed. In this problem the sum is five.
Step 3: Add cubes to get to the total. . I’ll use a different color, red, to do this.
Watch… I have 1, 2 yellow. If I add one more I’ll have 3. That’s not enough. If I
add another, I’ll have four. That’s still not enough. If I add another, I’ll have
five. That is the total I need.
Step 4: Count the number of cubes added to find the missing addend. I added 3
red cubes. 3 is the missing addend in this number sentence. If I add 3 cubes to the
2 cubes I began with, the sum is 5.
o Aligned Activity – Now it is your turn to follow the steps to find out how many cubes you
need to add to a given addend to find a sum. Have students use cubes and mats to
demonstrate the concept of how many more is needed (missing addend) to find given
sums:
 I have 3 cubes, but I need 7. How many more do I need?
 I have 5 cubes, but I need 10. How many more do I need?
 I have 1 cubes, but I need 3. How many more do I need?
 I have 3 cubes, but I need 4. How many more do I need?
 I have 6 cubes, but I need 9. How many more do I need?

Subobjective 2: TSW use pictures to represent the concept of missing addend or “How
many more is needed?”.
o Input- Today we will draw pictures to help us figure out the missing addend in a number
sentence. We will follow the same steps that we used yesterday.
o Modeling-. Watch as I solve to find the missing addend. I have 3 carrots, but I need 8.
How many more carrots do I need?
Step 1: Draw tally marks to represent known number of objects. III
1
Step 2: Write the total needed. 8
Step 3: Count up to the total. Add tally marks as you count. 4, 5, 6, 7, 8 IIIII
Step 4: Count the number of tallies added to find the missing addend. I added 5
tallies. 5 is the missing addend in this number sentence. If I add 5 tally marks to
the 3 I began with, the sum is 8.
o Aligned Activity- Give students individual white boards. Present a problem and
direct students to follow the steps to find the missing addend:
I have 7, but I need 8. How many more do I need?
I have 0, but I need 5. How many more do I need?
I have 2, but I need 7. How many more do I need?
I have 4, but I need 10. How many more do I need?
I have 6, but I need 8. How many more do I need?

Subobjective 3: Students will solve to find the missing addend in addition number sentences
for sums through 10.
o Input- Today we will solve addition number sentences like this 4 + ____ = 6 to find the
missing addend.
o Modeling- Watch as I solve the problem
Step 1: Begin with the known addend. I’ll put 4 in my head
Step 2: Count up until you reach the sum. I’ll hold up fingers to show how many I
count up. 5, 6. I have two fingers. I counted up two.
Step 3: Fill in the missing addend. The missing addend is 2. 4 + 2 + 6.
o Aligned Activity- Have students follow the same steps to solve for the missing addend in
addition number sentences like the following. Students can use individual whiteboards to
display the answer when the teacher gives the signal or the activity can be completed
using paper and pencil.
1 + ____ = 6
2 + ____ = 9
5 + ____ = 5
7 + ____ = 9
1 + ____ = 1
6 + ____ = 10
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