standard_description: 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.
problem_activity: Narrative
The purpose of this activity is for students to count their collection in a way that makes sense to them. Students are provided with 10-frames and counting mats to help them organize their collections. Students use appropriate tools strategically as they choose which tools help them count their collections (MP5). The purpose of the activity synthesis is to highlight that collections can be arranged in different ways, which will be useful in a future activity when students rearrange objects and notice that the total number of objects remains the same.
Required Materials
Materials to Gather
10-frames
Collections of objects
Counting mats
Required Preparation
Each student needs a collection of 11–20 objects.
Launch
Groups of 2
Give each student a collection of objects and access to 10-frames and a counting mat.
“How many objects are in your collection?”
Activity
3 minutes: independent work time
“Tell your partner how many objects are in your collection.”
30 seconds: partner discussion
“Switch collections with your partner. Do you agree with your partner about how many objects are in the collection?”
3 minutes: independent work time
Monitor for students who arrange their objects in different ways to count them.
Student Response
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Activity Synthesis
Invite previously identified students to demonstrate how they arranged and counted their collections.
“What do you notice about how they counted?”
If needed, “Each person arranged their objects in a different way, but they all counted each object one time.”
After each student shares, write or display the number and say “There are _____ objects in their collection.”


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