Lesson · Grade 3 · Mathematics
3D Objects: Faces, Edges and Vertices
- Grade 3
- Mathematics
- 1 min 26 s
- British Columbia
- BC3-MA-27
A see-through cube is the worked example: its faces are counted in pairs (2 + 2 + 2 = 6), its edges in fours (4 + 4 + 4 = 12) and its corners in fours (4 + 4 = 8), and a rectangular prism has the same numbers but rectangle faces, even after it is tipped onto its end. Then a cylinder, a cone and a sphere show their curved surfaces and their own counts, ending on the recap that faces, edges and vertices describe a 3D object.
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In one sentence
The question this lesson answers
How can we describe a 3D object, like this cube?
A face is a flat surface.
Transcript
What the lesson says
How can we describe a 3D object, like this cube?
A face is a flat surface.
An edge is where two faces meet.
A vertex is a corner.
A cube has 6 faces: top and bottom, front and back, left and right.
It has 12 edges: 4 on top, 4 on the bottom and 4 going up the sides.
It has 8 vertices: 4 on top and 4 on the bottom.
A rectangular prism also has 6 faces, 12 edges and 8 vertices.
But a cube's faces are all squares, and this prism's faces are rectangles.
Turning the prism does not change it: it still has 6 faces, 12 edges and 8 vertices.
A cylinder, a cone and a sphere each have a curved surface.
A cylinder has 2 flat faces, 2 curved edges and no vertices.
A cone has 1 flat face, 1 curved edge and 1 vertex at its tip.
A sphere has no flat faces, no edges and no vertices.
We describe a 3D object by its faces, edges and vertices.
Curriculum
Where this fits
- British Columbia, Grade 3
Mathematics, Geometry and measurement: construction of 3D objectsBC3-MA-27
Previous: Units of Time: From Seconds to YearsNext: Nets: Folding a Cube, Unfolding a Box
The outcomes and strands follow the British Columbia curriculum.
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