The shapes that people come across in their daily lives are generally three-dimensional shapes, also known as solids. Chapter 16, Understanding Three Dimensional Shapes, explains that an object is three dimensional if it is a figure with three dimensions, length, height, and width. In addition, to the length and breadth in 2D, it has a thickness or a depth. It also has three attributes, namely, face, edges, and vertices. The Cube and the Cuboids are the basic three-dimensional shapes. Three-dimensional shapes comprise both curve-shaped and straight-headed shapes.
The chapter also includes the relationship between cuboids and cubes. Each shape has a specific number of faces, edges, and vertices. For example, cuboids have 12 edges, 8 vertices and 6 faces. Similarly, cuboids that have all edges equal are known as cubes. However, all the three-dimensional shapes are formed by various two-dimensional shapes.
Objects which are around us can be classified into different shapes according to their properties. Chapter 16, Understanding Three Dimensional Shapes, also mentions briefly that three-dimensional shapes exist with curved surfaces like the surfaces of cones, spheres, and cylinders. For example, a sphere has one face with no edges and vertices. A pyramid is a well-known three-dimensional shape which is a polyhedron having a polygon base. Pyramids can consist of different bases. For example, a base with a triangular shape is known as a tetrahedron. The quadrilateral based, Pentagon based, and Hexagon based pyramids are called square pyramids, pentagonal pyramids and hexagonal pyramids, respectively. The chapter finally provides us with a brief mention of polyhedrons and their types based on the number of faces.