En anglais

Counting faces and picturing cross-sections

Mathématiques · Géométrie · de 11 à 13 ans

Nom ______________________ Date ____________

A square-based pyramid has five faces. How many vertices does it have?
Réponse : ______________
How many faces, edges and vertices does a triangular prism have?
- 5 faces, 9 edges, 6 vertices
- 6 faces, 12 edges, 8 vertices
- 5 faces, 8 edges, 5 vertices
- 4 faces, 6 edges, 4 vertices
How many vertices does a triangular prism have?
- 5
- 6
- 9
Slicing a cylinder straight across (horizontally) always produces a circle.
En entourer un : Vrai Faux
A triangular prism has 6 vertices. How many edges does it have?
Réponse : ______________
A net has 6 identical squares joined together. Which solid will it fold into?
- Cube
- Square-based pyramid
- Triangular prism
How many edges does a square-based pyramid have?
- 5
- 8
- 6
- 12
Tom says a net of 4 triangles folds into a square-based pyramid. Is Tom right?
En entourer un : Vrai Faux
A student says a net with 1 triangle and 3 rectangles will fold into a triangular prism. Is the net correct?
- No, a triangular prism needs 2 triangles and 3 rectangles, not 1 triangle
- Yes, that is exactly right
- No, a triangular prism needs 3 triangles and 3 rectangles
Which net folds into a triangular prism?
- Six squares
- One square and four triangles
- Four triangles
- Two triangles and three rectangles

Corrigé

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5 · Four base corners plus one apex give 5 vertices.
5 faces, 9 edges, 6 vertices · Two triangle ends plus three rectangles give 5 faces, 9 edges and 6 vertices.
6 · A triangular prism has 6 vertices: 3 on each triangular end. 9 is the edge count, not the vertex count.
Vrai · A horizontal slice runs parallel to the circular base, so the cross-section matches the base: a circle.
9 · A triangular prism always has 9 edges.
Cube · A cube has 6 square faces, so 6 squares is exactly the right number and shape to fold into one.
8 · Four base edges plus four sloping edges give 8.
Faux · Tom is wrong: 4 triangles make a triangular pyramid; a square base needs a square.
No, a triangular prism needs 2 triangles and 3 rectangles, not 1 triangle · A triangular prism has 2 triangular ends, not 1, so this net is missing a face.
Two triangles and three rectangles · A triangular prism needs exactly two triangle ends and three rectangular sides.