Question

Mark the correct alternative of the following:
The number of surfaces of a hollow cylindrical object is?
(a) 1
(b) 2
(c) 3
(d) 4

Answer 1

Hint: We are asked to count the number of surfaces of a hollow cylindrical object for that you have to draw a figure of a hollow cylindrical object then count the number of surfaces. Now, the surface is something which we can see and which we can touch or something which is not hidden. For e.g. an empty glass of water has two surfaces one inner and one outer. Similarly, you can count the number of surfaces of a hollow cylindrical object. `

Complete step by step answer:
We have to find the number of surfaces of a hollow cylindrical object. For that we are first of all drawing a hollow cylindrical object.
In the below figure, we have drawn a hollow cylindrical object with inner and outer radius to visualize the distinction between the inner and outer surface of the cylinder.

In the above diagram, you can see the two kinds of radius inner (AO) and outer (DP) and the space between inner and outer cylinder is filled. Now, the cylinder is empty meaning in the inner radius of the cylinder there is filled with nothing. So, we have two curved surface areas, outer and inner curved surface area is present. Apart from that we have two more surfaces, as you can see from the above figure, two rings, one lies at the bottom of the cylinder and one lies at the top.
From the above figure and the discussion that we just had we come to a conclusion that a hollow cylindrical object has a total of 4 surfaces; inner and outer curved surface areas and the ring lies at the base of the cylinder and the top of the cylinder.

So, the correct answer is “Option D”.

Note: In the above hollow cylinder, if we fill the inside of the hollow cylinder then the cylinder becomes solid then three surfaces are possible and those surfaces are, the outer curved surface area, the top and bottom circular bases of the solid cylinder.
Also, the real life examples of the hollow cylinder that we see in our everyday life are straw and water tanks that you see on the roof of the building or many more.