standard_description: Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
problem_activity: Narrative
The purpose of this activity is for students to produce written numbers for a given quantity represented in different ways. Some representations show the tens on the left and others show the ones on the left. Students must attend to the units in each representation and the meaning of the digits in a two-digit number, rather than always writing the number they see on the left in a representation in the tens place and the number they see on the right in a representation in the ones place (MP6).
Engagement: Develop Effort and Persistence.
Chunk this task into more manageable parts. Check in with students to provide feedback and encouragement after each chunk.
Supports accessibility for: Attention, Social-Emotional Functioning
Required Materials
Materials to Gather
Connecting cubes in towers of 10 and singles
Launch
Groups of 2
Give students access to connecting cubes in towers of 10 and singles.
Activity
Read the task statement.
“You will work on your own to start. When you and your partner are finished, compare your work.”
5 minutes: independent think time
3 minutes: partner discussion
Student Facing
Write the number that matches each representation.
1 ten 4 ones
Number: ____________
[IMG]
Number: ____________
9 tens
Number: ____________
\(20 + 5\)
Number: ____________
[IMG]
Number: ____________
\(7 + 40\)
Number: ____________
2 ones 8 tens
Number: ____________
[IMG]
Number: ____________
\(1 + 40\)
Number: ____________
[IMG]
Number: ____________
Student Response
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Activity Synthesis
Invite students to share the two-digit number that matches each representation and explain how it matches.


aligns: no