# RD Sharma Solutions for Class 8 Maths Chapter 21: Mensuration-II (Volumes and Surface Areas of a Cuboid and a cube)

The chapter deals with the area of a general idea of a cube or a cuboid. The chapter introduces the students to the concept of 3D figures and how to visualise them. The chapter defines the volume of a figure. It is the space or the region that has been enclosed by the faces of any figure. In other words, it can be defined as the amount of matter that can be filled within a shape.

The chapter also teaches the students about the concept of surface area. The surface area is the total area of all the faces of the figure (cube and cuboid). The 3D shapes are defined as items that take up space and have three dimensions: length, width, and height. The cubes and cuboids are the shapes present all around us in the form of dice, boxes, or even your rectangular tv remote. The total of the areas of all of the solid's faces or exterior portions determines its surface area. The capacity of a solid form or the space within the figure is known as the volume of a solid. The following are the formulae and techniques for calculating the volume and surface area of such shapes:

If a cuboid's height is h, length is l, and width is w, its surface area equals 2 (w * h + h * l + l * w) = 2 (wh + hl + lw). The volume of a cuboid with height = h, length = l, and width = w is given by l * b * w. A cube is a specific form of a cuboid with the same length, breadth, and heights, i.e., h = l = b, its volume is  side3. Because a cube has 6 square sides, its surface area equals 6a2 as its faces are equal.