Chapter 20 – Volume and Surface Area of Solids – R S Aggarwal Solutions for class 8
There are two surface areas:
1) Curved surface area: It is the area of all curved region of a solid excluding the top and base area. It is also known as lateral surface area. It is also area of four walls.
2) Total surface area: It includes the curved surface area and area of top and base of solid.
Volume: It is the total space occupied by a solid. It is measured in cubic units.
Formulas to be used in this chapter:
(1) Cuboid: It is a solid that have six rectangular plane faces.
- Volume of Cuboid = Length × breadth × height = (l×b×h) cubic units
- Curved surface area of cuboid = 2h (l + b) sq. units
- Total surface area of cuboid = 2(l b + b h + h l) sq. units
- Diagonal of a cuboid = l2+b2+h2 units
(1I) Cube: It is a solid in which length, breadth end height are equal. It is formed by six identical or congruent squares. Let ‘a’ be the edge of cube.
(a) Volume of Cube = (edge)3=a3 cubic units
(b) Curved surface area of cube = 4 a2sq. units
(c) Total surface area of cuboid = 6a2sq. units
(d) Diagonal of a cube = 3 a units