## RD Sharma Class 8 Solutions Chapter 21 - Mensuration II - Volumes Surface Area Cuboid and A Cube (Ex 21.2) Exercise 21.2 - Free PDF

## FAQs on RD Sharma Class 8 Solutions Chapter 21 Mensuration II - Volumes Surface Area of Cuboid and Cube Exercise 21.2

**1. What is a cuboid and how is it different from a rectangle?**

Cuboid is a polygon represented in three-dimensional format on a plane surface. It has 6 surface areas similar to that of a rectangle. The rectangle is a quadrilateral with four sides, four angles and four vertices. The opposite sides of a rectangle are equal and all angles measure 90 degrees. A cuboid is a 3-D representation of a rectangle with length, breadth and perpendicular height. The rectangle is a 2D figure with only length and breadth. Gift boxes are the best example of a cuboid and a cot is the best example of a rectangle.

**2. What is the formula to find the total surface area of a cuboid and cube?**

Cuboid has 6 surface areas, 8 vertices and 12 edges. RD Sharma chapter 21 class 8 has many problems related to finding out the total surface area of a cuboid and mentions the formula for it:

The total surface area of a cuboid is represented by T.S.A.

T.S.A. of cuboid = 2(lb + bh +lh)

where,

h = perpendicular height from the base

l = length of the cuboid

b = breadth of the cuboid

Similarly, the total surface area of a cube is represented by T.S.A.

T.S.A of cube = 6a^{2}

All the sides of a cube are equal as a cube is a 3D representation of a square

Here a = length of the side

**3. What is the formula to find out the lateral surface area of a cuboid and its perimeter?**

Lateral surface area is represented by L.S.A

L.S.A of cuboid = 2h(l + b)

l = length ; b= breadth; h = perpendicular height

Similarly, the perimeter of a cuboid is represented by P

P = 4(l+b+h)

l= length; b = breadth, h = perpendicular height

**4. What is the formula to find out the volume of a cuboid and a cube?**

Cuboid and cubes are polygons represented in three-dimensional format on a plane surface. RD Sharma chapter 21 class 8 has many problems related to finding out the volume of a cuboid and mentions the formula for the same:

The volume of the cuboid is represented by V

V = l x b x h

l= length, b= breadth, h= height

Similarly, the volume of a cube represented by V

V = a^{3}

a= length of side .