Describing 2D shapes
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Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about describing how 2D shapes look.
Task administration:
This task can be completed with pen and paper or online (with some auto marking).
Students should have already had opportunties to look at the attributes of 2dimensional shapes.
Copyright:
NZCER created graphics
Level:
2
Curriculum info:
Keywords:
Description of task:
Students give the number of vertices, straight lines, and curved lines and complete sentences to describe different 2dimensional shapes.
Curriculum Links:
This resource can be used to help to identify students' understanding of identifying nets for cubes.
Learning Progression Frameworks
This resource can provide evidence of learning associated with within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.Answers/responses:
Y4 (10/2013)


a) 
12 straight lines
0 curved lines
12 corners
Responses that:

easy
easy
moderate
moderate

b) 
0 straight lines
2 curved lines 2 corners Responses that:

very easy
very easy
very easy
moderate

c) 
2 straight lines
2 curved lines 4 corners Responses that:

very easy very easy very easy moderate 
d) 
7 straight lines
0 curved lines 7 corners
Responses that:

easy
easy
moderate
moderate

e) 
4 straight lines
0 curved lines 3 corners
Responses that:

very easy
very easy
easy
difficult

Based on a online sample of 34 Year 4 students.
Likely misconception  Next steps  
a) 8 (or 4) corners
b) 5 (or 2) corners

Students only count the number of convex corners/vertices (8 and 5 respectively) and ignore the concave corners/vertices (4 and 2 respectively).
4 and 2 corners respectively means only the concave corners/vertices are counted.

Students could discuss what it means to be a corner: where any two lines meet.
Encourage the students to give their own descriptive names to the two kinds of corners/vertices:

a) 4 curved lines (with 4 straight lines)
d) 2 curved lines

Students may see the concave corners of a shape as "bent" or curved lines.  Students could discuss what is means to have straight and curved lines, and explore a range of examples (in pairs or groups). 
Teaching and learning:
This resource asks students to count the number of lines and corners (vertices) of shapes, and to describe what else they notice about the shapes.
Diagnostic and formative information:
Likely misconception  Next steps  
a) 8 (or 4) corners
b) 5 (or 2) corners

Only counts the number of convex vertices (8 and 5 respectively) and ignores the concave vertices (4 and 2 respectively).
4 and 2 corners respectively means only the concave corners are counted.

Discuss what it means to be a corner. This is where any two lines meet.
Encourage the students to give their own names to the two kinds of verticies:
 concave could be "bending in", "like a cave"
less than a straight line (180 degrees)
 convex could be "bending out", "ex is exterior"
more than a straight line (180 degrees) 
a) 4 curved lines
d) 2 curved lines

May see the concave parts of the shape as curved lines.  Discuss the meaning of straight lines, and curved lines. 
a) 4 straight lines  May see the shape as a square 
Discuss the meaning of straight lines and curved lines.

a)  e) Other errors  Various 
Discuss the meaning of straight lines and curved lines, and corners (where lines meet). 
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 Puzzling shapes III
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 Describing shapes
 Projecting shapes
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 Corners, faces and edges III
 Whetu's frame
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 Corners and sides II
 Triangle or not?
 What Shape am I?
 Square or not?
 Rectangle or not?
 Sorting shapes II
 Look at the shapes