standard_description: Determine the unknown whole number in an addition or subtraction equation relating to three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = �� – 3, 6 + 6 = ��.
problem_activity: Narrative
The purpose of this activity is for students to consider two different equations that represent the same story problem. Put Together, Result Unknown problems help students make sense of the commutative property because the two parts can be combined in different orders. This property, as well as the associative property, is referred to as “add in any order” to students. Students contextualize the problem and see that each number represents a specific object’s quantity, no matter which order it is presented, and connect these quantities to written symbols (MP2). Students will work more with the “add in any order” property in future lessons.
Representation: Access for Perception.
Students may benefit from hearing the instructions read aloud more than once.
Supports accessibility for: Language, Attention
Required Materials
Materials to Gather
10-frames
Connecting cubes or two-color counters
Launch
Groups of 2
Give students access to 10-frames and connecting cubes or two-color counters.
“We just solved a problem about pet fish. What else do you know about pets?”
30 seconds: quiet think time
1 minute: partner discussion
If needed ask, “What kinds of pets are there?”
Activity
Read the task statement.
3 minutes: independent work time
2 minutes: partner discussion
Monitor for a student who uses objects or drawings to show that each equation matches the story.
Student Facing
Tyler and Clare want to know how many pets they have together.
Tyler has 2 turtles.
Clare has 4 dogs.
Tyler wrote the equation
\(4 + 2= \boxed{6}\)
.
Clare wrote the equation
\(2 + 4 = \boxed{6}\)
.
Do both equations match the story?
Why or why not?
Show your thinking using drawings, numbers, or words.
Student Response
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Advancing Student Thinking
If students explain that both equations match the story using only numbers, consider asking:
"How do you know that both equations match the story?"
"How could you use connecting cubes to show that they both match?"
Activity Synthesis
Invite previously identified students to share.
“How does their work show us that Tyler’s equation matches the story?”
“How does their work show us that Clare’s equation matches the story?”


aligns: no