Describing 2-D shapes

Describing 2-D shapes

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about describing how 2-D shapes look.

Question 1Change answer

a)  Complete the sentences about the shape below.
many sided shape
This shape has  straight sides,  curved sides, and  corners.
What else do you notice about the shape?

Question 1Change answer

b)  Complete the sentences about the shape below.
curved shape
This shape has  straight sides,  curved sides, and  corners.
What else do you notice about the shape?

Question 1Change answer

c)  Complete the sentences about the shape below.
another curved shape
This shape has  straight sides,  curved sides, and  corners.
What else do you notice about the shape?

Question 1Change answer

d)  Complete the sentence about the shape below.
arrow shape
This shape has  straight sides,  curved sides, and  corners.
What else do you notice about the shape?

Question 1Change answer

e)  Complete the sentence about the shape below.
lined shape
This shape has  straight sides,  curved sides, and  corners.
What else do you notice about the shape?
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 2-dimensional shapes.
Copyright: 
NZCER created graphics
Level:
2
Curriculum info: 
Maths, Geometry and Measurement, Shape
Keywords: 
2-dimensional shapes, shape properties, edges, vertices
Description of task: 
Students give the number of vertices, straight lines, and curved lines and complete sentences to describe different 2-dimensional 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
Geometric thinking, set 3
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:
  • say what it is such as; "It's a cross" or "It's a health symbol " OR
  • state other features of the shape (not lines or corners) e.g., "It is blue".
easy
easy
moderate
moderate
b)
0 straight lines
2 curved lines
2 corners
Responses that:
  • say what it looks like such as "It looks like a moon... a banana ... a smile"
  • state other features of the shape (not lines or corners) e.g., "It is green".
very easy
very easy
very easy
moderate
c)
2 straight lines
2 curved lines
4 corners
Responses that:
  • say what it looks like such as "It looks like a rainbow ... a half donut ... a tunnel"
  • state other features of the shape (not lines or corners) e.g., "It is red".
 very easy
very easy
very easy
moderate
d)
7 straight lines
0 curved lines
7 corners
Responses that:
  •    say what it is looks like such as "It's an arrow";
  •    state other features of the shape (not lines or corners) e.g., "It is purple".
easy
easy
moderate
moderate
e)
4 straight lines
0 curved lines
3 corners
Responses that:
  • say that it is not a closed shape such as "It has a bit missing ... it is broken";
  • say what it looks like such as "It looks like a roof ...  a sort of rectangle";
  • state other features of the shape (not lines or corners).
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:
  • 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 (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).