- 3D shapes/objects are those which do not lie completely in a plane.
- 3D objects have different views from different positions.
- A solid is a polyhedron if it is made up of only polygonal faces, the faces meet at edges which are line segments and the edges meet at a point called vertex.
- Euler’s formula for any polyhedron is, F + V – E = 2 Where F stands for number of faces, V for number of vertices and E for number of edges.
- Types of polyhedrons: (a) Convex polyhedron A convex polyhedron is one in which all faces make it convex.
- A polyhedron is regular if its faces are congruent regular polygons and the same number of faces meet at each vertex.
- For example, a cube is a platonic solid because all six of its faces are congruent squares.
- There are five such solids– tetrahedron, cube, octahedron, dodecahedron and icosahedron.
- A prism is a polyhedron whose bottom and top faces (known as bases) are congruent polygons and faces known as lateral faces are parallelograms (when the side faces are rectangles, the shape is known as right prism).
- A pyramid is a polyhedron whose base is a polygon and lateral faces are triangles.
- A map depicts the location of a particular object/place in relation to other objects/places.
- Scale is the relationship between the drawing’s/model’s dimensions to the actual object’s dimensions.
- In a map, symbols are used to depict the different objects and places.
- Maps involve a scale which is fixed for a particular map

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