Chapter 20 Mensuration deals with areas and perimeters of the shapes and figures. Every figure has its area and perimeter, depending on its size. It is used to study the calculations of geometric figures. There are few important terms: area, perimeter, volume, and curved surface area explained in this chapter. The surface (region), which is enclosed by a boundary, is denoted as the area of that particular figure.
Similarly, the space occupied by any of the three-dimensional shapes is referred to as the volume of the shape. The curved surface area is only the area of the curved surface, excluding the top and base of the shape. The total area covering the sides of the shape (excluding the top art and the base) is known as the lateral area of the surface. The total surface area is the sum of both curved and lateral surface areas.
Chapter 20 Mensuration further discusses the list of formulas available for calculating various measures of a body. There are different formulas to calculate the measurement for each of the shapes. For example, the area of a square is a2, whereas the perimeter can be found by 4a, where 'a' is the measurement of sides. The most important fact is that when the square side is halved, the area becomes one-fourth of its previous value.
The rectangle area is l*b, and the perimeter is 2 (l + b). There are two types of units: square unit (used for the area) and cubic unit(used for volume). Most of the mensuration problems can be solved by these formulas, and a unit must be included at the end. Areas can be compared for two figures as well.
Finally, the chapter provides a brief introduction to the calculations related to three-dimensional shapes. For example, for 3-D shapes such as a cube, the area can be found by calculating the area of all the faces.