standard_description: Use the definition of congruence in terms of rigid motions to show that two triangles are congruent if and only if corresponding pairs of sides and corresponding pairs of angles are congruent.
problem_activity: Narrative
The purpose of this activity is for students to make sense of different methods they can use to compare three-digit numbers. They analyze the thinking of others and make connections across representations (MP2, MP3). Although students have compared numbers using different representations in prior units, this activity offers them the opportunity to consider using the number line as a tool to compare three-digit numbers. In the synthesis, students will discuss which representation makes it easier to see the comparison. While students could make a case that each of the representations was easier for them, the focus is on Jada’s way, the number line.
MLR8 Discussion Supports.
Display sentence frames to support partner discussion. “_____ and _____ are the same/alike because . . .” and “_____ and _____ are different because . . . .”
Advances: Speaking, Conversing
Launch
Groups of 2
Activity
“Diego, Jada, and Clare were asked to compare 371 and 317. They each represented their thinking differently.”
“Take some time to look over their methods.”
2 minutes: independent work time
“Discuss with your partner how their methods are the same and different.”
4 minutes: partner discussion
“Now try Jada’s way.”
6 minutes: partner work time
Student Facing
Each student compared 371 and 317, but represented their thinking in different ways.
Diego
[IMG]
[IMG]
I see 3 hundreds for each number.
317 only has 1 ten, but 371 has 7 tens.
\(371 > 317\)
Clare
Each has 3 hundreds.
371 has 7 tens, but 317 only has 1 ten.
\(317 < 371\)
Jada
[IMG]
I can see that 371 is farther to the right on my number line, so I know it is greater than 317.
\(371 > 317\)
What is the same and different about these students’ representations?
Discuss with a partner.
Try Jada’s way.
Estimate the location of 483 and 443 on the number line.
Mark each number with a point. Label the point with the number it represents.
[IMG]
Use
\(>\)
,
\(=\)
, or
\(<\)
to compare 483 and 443.
______________________________
Student Response
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Advancing Student Thinking
If students write comparison statements that are not true, ask them to read their statements and consider asking:
“How did you decide which number was greater?”
“How does your statement match the number line?”
Activity Synthesis
“Clare, Diego, and Jada represented their thinking in different ways. Whose method made it easier to see that 371 is greater than 317? Explain.” (Jada’s because you just have to look at which number is farther to the right. You can see 371 is farther from 0. Diego’s because I use diagrams and I can see quickly that the hundreds are the same and there are more tens, but some things were the same.)
As needed, “Jada and Diego wrote
\(371 > 317\)
, but Clare wrote
\(317 < 371\)
. Who do you agree with? Explain.” (They both mean the same thing. 371 is greater than 317, so 317 is less than 371.)


aligns: no