standard_description: Solve word problems involving addition and subtraction of fractions referring to the same whole, including cases of unlike denominators, e.g., by using visual fraction models or equations to represent the problem. Use benchmark fractions and number sense of fractions to estimate mentally and assess the reasonableness of answers. For example, recognize an incorrect result 2/5 + 1/2 = 3/7, by observing that 3/7 < 1/2.
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have for making 10 when adding. These understandings help students develop fluency with operations within 20.
When students look for ways to rearrange and decompose numbers to make 10, they notice and make use of structure of expressions and whole numbers (MP7).
Launch
Display one expression.
“Give me a signal when you have an answer and can explain how you got it.”
1 minute: think time
Activity
Record answers and strategies.
Keep expressions and work displayed.
Repeat for each expression.
Student Facing
Find the value of each sum mentally.
\(4 + 8 + 2\)
\(4 + 5 + 3 + 2\)
\(9 + 3 + 1\)
\(9 + 5\)
Student Response
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Activity Synthesis
“How did making a ten help when finding the sums?”


aligns: no