standard_description: Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.
problem_activity: Narrative
The purpose of this activity is for students to connect written multiples of 10 to base-ten representations. Students notice a connection between how the numbers are said, written, and represented with tens. For example, “70” has the word “seven” as it is said, the digit “7” when it is written, and is represented with seven tens. Each number name is written under the number in this activity. Students are not expected to spell number names.
MLR8 Discussion Supports.
Invite students to begin partner interactions by repeating the question, “How did you match the towers of 10 to the written numbers?” This gives both students an opportunity to produce language.
Advances: Conversing
Required Materials
Materials to Gather
Connecting cubes
Materials to Copy
It's a Match (10-90) words, numbers, pictures
Launch
Groups of 2
Give each student a blackline master and access to connecting cubes.
Activity
Read the task statement from the blackline master.
5 minutes: independent work time
3 minutes: partner discussion
Monitor for students who count the number of towers, match correctly, and can explain how they knew.
Student Response
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Activity Synthesis
Invite previously identified students to share.
“How did you know which representations matched?” (I counted by ten and found the number. I said 10, 20, 30, 40, 50, and found 50.)


aligns: no