standard_description: Prove that, given a system of two equations in two variables, replacing one equation by the sum of that equation and a multiple of the other produces a system with the same solutions.
problem_activity: Narrative
The purpose of this How Many Do You See is for students to subitize or use grouping strategies to describe the images they see.
When students notice that dots are being added on with each image, they look for and make use of structure (MP7).
Launch
Groups of 2
“How many do you see? How do you see them?”
Flash image.
30 seconds: quiet think time
Activity
Display image.
“Discuss your thinking with your partner.”
1 minute: partner discussion
Record responses.
Repeat for each image.
Student Facing
How many do you see?
How do you see them?
[IMG]
[IMG]
[IMG]
[IMG]
Student Response
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Activity Synthesis
Display the first and third images.
“What changed from the first group of dots to the third group of dots.” (2 more dots were added.)
“The third group has 4 dots and 2 more dots. We can write that as ‘4 and 2’ or ‘
\(4 + 2\)
’.”


aligns: no