Question

How many surfaces are there in a solid cylinder?
(A) 1
(B) 2
(C) 3
(D) 4

Answer 1

Hint: We know that a surface is a continuous set of points that can have length and breadth, or radius but no thickness. The top and bottom portion of the cylinder has some radius and also no thickness. So, the top and the bottom portion of the cylinder are surfaces of the cylinder. We also know that a surface is the uppermost layer of the physical object. So, the front side is also a curved surface of the cylinder. Now, calculate the total number of surfaces of a cylinder.

Complete step-by-step answer:
According to the question, we have a cylinder and we have to find all the surfaces present in a cylinder.
Let us observe all the surfaces of the cylinder using a diagram.

We know that a surface is a continuous set of points that can have length and breadth, or radius but no thickness.
In the figure, we can observe that the upper portion present at the top of the cylinder has some radius. So, we can say that there is a circular type flat surface present at the top of the cylinder.
Similarly, we can observe that the lower portion present at the bottom of the cylinder has some radius. So, we can say that there is a circular type flat surface present at the bottom of the cylinder.
Therefore, we have two circular flat surfaces in a cylinder.
Now, we can observe that there is also one more surface present in the cylinder. That is the surface present at the front. The curved surface of the cylinder. So, here, we got one more surface.
Now, we have three surfaces, circular flat surface at the top, circular flat surface at the bottom, and the curved surface at the front.
Therefore, the total number of surfaces in a cylinder is 3.
Hence, the correct option is (C).

Note: In this question, one might make a silly mistake and miss the point that the front side of a cylinder is also a surface. The front side of a cylinder that is the curved surface is also a surface because the surface is also the uppermost layer of the physical object.