standard_description: Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l). (Excludes compound units such as cm^(3) and finding the geometric volume of a container.) Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem. [Excludes multiplicative comparison problems (problems involving notions of “times as much”)]
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have for adding groups of 2 and groups of 5. These understandings help students develop fluency and will be helpful later in this lesson when students need to be able to use data in scaled bar graphs to solve one- and two-step “how many more” and “how many fewer” problems. Students use the structure of the expressions and repeated reasoning when they use methods based on skip-counting by 2 or 5 or counting on 2 or 5 from a previous known value (MP7, MP8).
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 expression mentally.
\(2 + 2 + 2 + 2 + 2\)
\(2 + 2 + 2 + 2 + 2 + 2\)
\(5 + 5 + 5 + 5 + 5 + 5\)
\(5 + 5 + 5 + 5 + 5 + 5 + 5\)
Student Response
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Activity Synthesis
“What is a strategy that you hadn’t used before that you might use in the future?” (Thinking about one more group if I already know part of the problem. Skip-counting.)
Consider asking:
“Who can restate _____’s reasoning in a different way?”
“Did anyone have the same strategy but would explain it differently?”
“Did anyone solve the problem in a different way?”
“Do you agree or disagree? Why?”


aligns: no