standard_description: Recognize angle measure as additive. When an angle is decomposed into non-overlapping parts, the angle measure of the whole is the sum of the angle measures of the parts. Solve addition and subtraction problems to find unknown angles on a diagram in real world and mathematical problems, e.g., by using an equation with a symbol for the unknown angle measure.
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have for making a ten to add. When students look for ways to decompose an addend to make 10, students look for and make use of the structure of numbers and the properties of operations (MP7). These understandings help students develop fluency and will be helpful later in this lesson when students will need to be able to add within 20.
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 strategy.
Keep expressions and work displayed.
Repeat with each expression.
Student Facing
Find the value of each sum mentally.
\(8 + 2\)
\(8 + 3\)
\(8 + 5\)
\(7 + 6\)
Student Response
Teachers with a valid work email address can
click here to register or sign in
for free access to Student Response.
Activity Synthesis
“How does making 10 help in finding the value of the sums?” (It helped me because I was able to use facts I already know. I know
\(7 + 3 = 10\)
and I know
\(10 + 3 = 13\)
.)


aligns: no