standard_description: Apply properties of operations as strategies to add and subtract. (Students need not use formal terms for these properties.) Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have for making a ten when adding within 20. The numbers chosen lend themselves to making a ten to find the value of the sum. These understandings help students develop fluency and will be helpful later in this lesson when students make a ten when adding one-digit numbers and two-digit numbers.
Launch
Display one expression.
“Give me a signal when you have an answer and can explain how you got it.”
1 minute: quiet think time
Activity
Record answers and methods.
Keep expressions and work displayed.
Repeat with each expression.
Student Facing
Find the value of each expression mentally.
\(8 + 2\)
\(8 + 5\)
\(9 + 8\)
\(7 + 6\)
Student Response
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Activity Synthesis
“How could
\(8 + 2\)
help you to find the value of
\(8 + 5\)
?” (I can add 2 to 8 to get to 10, and then I have 3 more to add.
\(10 + 3\)
is 13.)


aligns: no