Mensuration is about the length, volume or area of different geometric shapes. These shapes exist in 2 dimension or 3 dimensions. This unit is concerned only about mensuration in three dimensional. The three dimensional (3D) shapes can be described in terms of their faces, vertices and edges. Face is a flat curved surface; edge is a line where two faces meet; and vertex is a point where three or more edges meet. In this unit we consider mensurations of the following three dimensional shapes: Prisms, Cones, pyramids, and Sphere.