Introduction

Observe the following figures

Have you noticed any differences between the figures in first line and second line?

The figures in first line can be easily drawn in our notebooks. These figures have only length and breadth and are known as D objects.

On the other hand, the figures in group (b) have length, breadth, and height, making them D objects, also called solid figures. These solid figures are commonly found in our surroundings.

You have already learned about plane figures and their areas. Now, we will explore the surface areas and volumes of three-dimensional objects, such as cylinders, cones, and spheres.