Activity:
To Triangle or Not to Triangle |
Teacher's Page
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Part 1 - Making
Triangles
Below are 12 line segments (or straws) of various length.
Make as many unique triangles as you can using these
segments. Click on image below to launch the app.
After you make your triangles, record them in the table
below.
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length A
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length B
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length C
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What kind of
triangle is it? |
1 |
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2 |
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3 |
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4 |
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5 |
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6 |
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Part 2 - Making “Untriangles”
We know that a triangle has three sides that form a
closed shape. But what’s an "untriangle?"
Below is an example of an untriangle. Why do you think its
called an untriangle?
Make and record your untriangles below:
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length A
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length B
|
length C
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Why is this an
untriangle? |
1 |
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2 |
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3 |
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4 |
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Below are candidates for “trianglehood.”
Indicate which are the triangles which are “wannabe”
triangles (untriangles).
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length A
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length B
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length C
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Triangle (T) or
untriangle (U)? |
Explain why T or U? |
a |
2
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3
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4
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b |
8
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4
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2
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c |
6
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6
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6
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d |
7
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4
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3
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e |
3
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6
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3
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f |
8
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6
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6
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g |
2
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3
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2
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h |
2
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5
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2
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i |
8
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7
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6
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j |
3
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4
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5
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Some Questions:
1. If two of the two line segments are equal will you
always be able to make a triangle with the third stick?
Explain.
2. How about if all the segments are the same length? Can
you always make a triangle? What is this triangle called?
3. Explain when it is possible for you to make a triangle
with three segments.
4. Explain when it is NOT possible for you to make a
triangle with three segments.
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