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3D Shape Edge Count Quiz: Cuboid, Cone, Square-based Pyramid
Mathematics
Grade 3 of Primary School
Question Content
2. How many edges do the following 3-D shapes have? a) Cuboid ______ edge(s) b) Cone ______ edge(s) c) Square-based pyramid ______ edge(s)
Correct Answer
a) 12; b) 1; c) 8
Detailed Solution Steps
1
Step 1: Recall the definition of an edge (a line segment where two faces of a 3D shape meet):
2
Step 2: For a cuboid: A cuboid has 12 edges, with 4 edges for each of the 3 sets of parallel edges (length, width, height).
3
Step 3: For a cone: A cone has only 1 edge, which is the curved edge where the flat circular base meets the curved lateral face.
4
Step 4: For a square-based pyramid: It has a square base with 4 edges, plus 4 edges connecting the base vertices to the apex, so total 4 + 4 = 8 edges.
Knowledge Points Involved
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3D Shape Edges (Cuboid)
A cuboid is a rectangular 3D shape with 12 straight edges, grouped into 3 pairs of 4 equal-length parallel edges. This is a core property for identifying and measuring cuboid structures.
2
3D Shape Edges (Cone)
A cone is a 3D shape with a circular base and a single apex. It has only 1 curved edge where the base and lateral surface meet, no straight edges.
3
3D Shape Edges (Square-based Pyramid)
A square-based pyramid has a square base (4 edges) and 4 triangular faces that meet at an apex, adding 4 more edges, totaling 8 edges. This applies to counting edges in pyramid-shaped 3D objects.
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