Surface area of a solid is the sum of the areas of its faces.

The surface area of a solid is a measure of the total area of all the surfaces or faces of the solid. It can be thought of as the amount of material needed to cover the entire surface of the solid.

Explanation:

A solid object is three-dimensional and has length, width, and height. It is made up of multiple faces, which are two-dimensional shapes that form the boundaries of the solid. The surface area of a solid is the sum of the areas of all these faces.

For example, consider a cube. A cube has six faces, each of which is a square. To find the surface area of the cube, we need to calculate the area of each face and then sum them up.

The formula for finding the area of a square is side length squared. So, if the side length of the cube is 's', then the area of each face is s^2. Since there are six faces, the total surface area of the cube is 6s^2.

Similarly, for other solid objects such as rectangular prisms, cylinders, spheres, etc., the surface area is calculated by finding the area of each face and adding them together.

The surface area is an important concept in geometry and has practical applications in fields such as architecture, engineering, and manufacturing. It helps in determining the amount of material required to construct a solid object or the amount of paint needed to cover its surface.

In summary, the surface area of a solid is the sum of the areas of all its faces. It is a measure of the total area of the surface of the solid and is calculated by finding the area of each face and adding them together.