This is a rectangular prism which should be referred to as a cuboid. This 3D shape is a type of prism.Ĭ) i) For neither (polyhedron): This is an irregular polyhedron or a compound solid***. The cross-sectional areas are congruent as shown by these yellow rectangles. Imagine the net folding up into a 3D shape. The faces are not the same they are different size rectangles. The 3D shape it will form is therefore a polyhedron.Ģ Identify if all the faces are the same regular shape. What 3D shape can be formed from this net?Īll the 2D shapes that make up this net are polygons they are all rectangles. Ii) For neither (non-polyhedron): those needed to be named on the GCSE syllabus are spheres and hemispheres.Įxample 1: naming a 3D shape from its net I) If yes, this is one of the Platonic solids (tetrahedron, cube, octahedron, dodecahedron or icosahedron).Ī) a pyramid or cone (3D shape with a base, an apex and similar cross-sectional areas).ī) a prism or cylinder (3D shape with congruent cross-sectional areas).Ī) For pyramids: the name of the base shape often forms the name of the 3D shape.ī) For prisms: the name of the cross-sectional area often forms the name of the 3D shape.Ĭ) i) For neither (polyhedron): This is an irregular polyhedron or a compound solid. Identify if all the faces are the same regular shape. Here we will learn about 3D shapes names, including types of polyhedra (prisms, pyramids, platonic solids, irregular), non-polyhedra (cones. Ii) a non-polyhedron (includes a curved surface) – go to step 3. I) a polyhedron (all flat polygonal faces) – go to step 2. In order to categorise and name a 3D shape: So a frustum can also be described as a truncated pyramid or truncated cone. The mathematical term for ‘slicing off an apex’ is ‘truncating’. If the apex of a pyramid or cone is sliced off then the remaining shape is known as a frustum. However, unlike pyramids, cones do not have sloping triangular side faces but instead they have a curved side surface. Their cross-sectional areas are similar circles. The cross sectional areas of both right pyramids and oblique pyramids are similar to each other.Ĭones can be described like pyramids they have a circular base shape and an apex. This is illustrated in the diagrams below. If the apex of the pyramid does not lie directly on top of the centre of the base, the pyramid is an oblique pyramid. If the apex of the pyramid lies directly on top of the centre of the base, the pyramid is a right pyramid. The lateral edges may be different in length.įor all types of pyramids the cross sectional areas are similar to each other as illustrated in the diagrams below. The base shape of an irregular pyramid is an irregular polygon (a 2D shape with straight sides which vary in length). The base shape of a regular pyramid is a regular polygon (A 2D shape with straight equal sides).Īll the lateral edges (edges leading from the base to the apex) are equal in length. It has triangular side faces which slope to meet each other at the apex. A pyramid is a polyhedron that has a flat polygonal base and an apex.
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