standard_description: Fluently add and subtract within 20 using mental strategies. (See standard 1.OA.6 for a list of mental strategies.) By end of Grade 2, know from memory all sums of two one-digit numbers.
problem_activity: Narrative
The purpose of this warm-up is to elicit the idea that number lines and tape diagrams can be used to represent the same relationships between numbers, which will be useful when students use tape diagrams and number lines in a later activity to interpret and solve story problems. While students may notice and wonder many things about these representations, the important discussion points are the way both representations show quantities and how they could be used to represent addition.
Launch
Groups of 2
Display the image.
“What do you notice? What do you wonder?”
1 minute: quiet think time
Activity
“Discuss your thinking with your partner.”
1 minute: partner discussion
Share and record responses.
Student Facing
What do you notice? What do you wonder?
[IMG]
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Student Response
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Activity Synthesis
“What equation do you think best matches these diagrams?” (
\(5+4=9\)
)
“Where do we see the 5 in both diagrams?” (the 5 on the number line is the distance from 0 to the point at 5)
“Where do you see the 4 in both diagrams?” (the 4 on the number line is the 4 spaces that were moved to the right)


aligns: no