Related Topics: More Geometry Lessons
A cube is a three-dimensional figure with six equal square sides. The figure below shows a cube. The dotted lines indicate edges hidden from your view.
If s is the length of one of its sides, then the area of each side of a cube is s2. Since a cube has six square-shape sides, its total surface area is 6 times s2.
Surface area of a cube = 6s2
A rectangular solid is also called a rectangular prism or a cuboid. In a rectangular solid, the length, width and height may be of different lengths.
The surface area of the above cuboid would be the
sum of the area of all the surfaces.
Total area of top and bottom surfaces is lw + lw = 2lw
Total area of front and back surfaces is lh + lh = 2lh
Total area of the two side surfaces is wh + wh = 2wh
Surface area of rectangular solid = 2lw + 2lh + 2wh = 2(lw + lh + wh)
A prism is a solid that has two parallel faces which are congruent polygons at both ends. These faces form the bases of the prism. The other faces are in the shape of rectangles. They are called lateral faces. A prism is named after the shape of its base.
The surface area of a prism is the sum of the area of all its external faces.
We can also use the formula
Surface area of prism = 2 × area of base + perimeter of base × height
A sphere is a solid in which all the points on the round surface are equidistant from a fixed point, known as the center of the sphere. The distance from the center to the surface is the radius.
Surface area of a sphere with radius r = 4 πr2
A cylinder is a solid that has two parallel faces which are congruent circles. These faces form the bases of the cylinder. The cylinder has one curved surface. The height of the cylinder is the perpendicular distance between the two bases.
The net of a solid cylinder consists of 2 circles and one rectangle. The curved surface opens up to form a rectangle.
Surface area = 2 × area of circle + area of rectangle
Surface Area = 2πr2 + 2πrh = 2πr (r + h)
Sometimes you may be required to calculate the total surface area of a hollow cylinder or tube.
Total surface area of hollow cylinder
= area of internal curved surface + area of external curved surface + area of the two rings
= 2πrh + 2πRh + 2(πR2 − πr2)
A cone is a solid with a circular base. It has a curved surface which tapers (i.e. decreases in size) to a vertex at the top. The height of the cone is the perpendicular distance from the base to the vertex.
The net of a solid cone consists of a small circle and a sector of a larger circle. The arc of the sector has the same length as the circumference of the smaller circle.
Surface area of cone = Area of sector + area of circle
= πrs + πr2 = πr(r + s)
A pyramid is a solid with a polygonal base and several triangular lateral faces. The lateral faces meet at a common vertex. The height of the pyramid is the perpendicular distance from the base to the vertex. The pyramid is named after the shape of its base.
We can find the surface area of any pyramid by adding up the areas of its lateral faces and its base.
Surface area of any pyramid = area of base + area of each of the lateral faces
If the pyramid is a regular pyramid, we can use the formula for the surface area of a regular pyramid.
where p is the perimeter of the base and s is the slant height.
Surface area of regular pyramid = area of base + ps
If the pyramid is a square pyramid, we can use the formula for the surface area of a square pyramid.
Surface area of square pyramid = b2 + 2bs
where b is the length of the base and s is
the slant height.