In geometry, a pentagonal prism is a three-dimensional shape with two pentagonal bases and five rectangular faces. So, a pentagonal prism has a total of 7 faces, 15 edges, and 10 vertices out of which 2 faces are pentagonal in shape. We can find the volume and surface area of a pentagonal prism as we do for any other 3D shape. Let's learn everything about pentagonal prism in detail in this article.
|1.||What is a Pentagonal Prism?|
|2.||Types of Pentagonal Prisms|
|3.||Pentagonal Prism Formulas|
|4.||Solved Examples on Pentagonal Prism|
|5.||Practice Questions on Pentagonal Prism|
|6.||FAQs on Pentagonal Prism|
What is a Pentagonal Prism?
A pentagonal prism is a three-dimensional solid that has two pentagonal bases - bottom and top. All the other sides of a pentagonal prism have the shape of a rectangle. It is easy to understand the shape of a pentagonal prism by drawing a pentagon on a piece of paper using straight lines. Then imagine it stretching up from the sheet of paper. The 3D shape so formed will be a pentagonal prism!
A pentagonal prism has:
- 7 faces
- 15 edges
- 10 vertices
- Pentagon bottom and top
Pentagonal Prism Examples
Here are some real-life examples of a pentagonal prism. Look at the figures given below and look around you to find more examples of pentagonal prism and make your own list.
- U.S. Defence Department Headquarter
- Barns and boxes
- Decorative items
Types of Pentagonal Prisms
Pentagonal prisms can be categorized into the following types:
- Regular pentagonal prisms
- Right pentagonal prisms
- Oblique pentagonal prisms
Regular Pentagonal Prisms
If all the sides of a pentagonal prism are equal in length, it is called a regular pentagonal prism. Note the following properties of a regular pentagonal prism.
- All rectangular faces of a regular pentagonal prism are congruent.
- When the pentagonal faces of a regular pentagonal prism are the bases, the rectangular faces of the prism are said to be lateral.
Right Pentagonal Prism
If the pentagon faces of a pentagonal prism are congruent and parallel, and the rectangular faces are perpendicular to the pentagon faces, it is called a right pentagonal prism.
Oblique Pentagonal Prism
If the pentagon faces of a pentagonal prism are not exactly on top of each other, that is, when the rectangular faces are not perpendicular to the pentagon faces, it's called an oblique pentagonal prism.
Pentagonal Prism Formulas
The formulas of a pentagonal prism help us to find out the surface area and its volume very quickly and easily. Observe the following figure where 'a' is the apothem length of the prism, 'b' is the base length, and 'h' is the height of the prism.
Surface Area of a Pentagonal Prism
The surface area of a pentagonal prism gives the area of each face of the prism. The formula for the surface area of a pentagonal prism is:
Surface Area = (5ab + 5bh) square units
Pentagonal Prism Volume
The volume of a pentagonal prism gives the capacity of the prism. The formula for the volume of a pentagonal prism is:
Volume = (5/2 × abh) cubic units
Example: If the apothem length 'a' of a pentagonal prism is 5 feet, the base length 'b' is 4 feet, and the height 'h' is 6 feet.
The surface area of the pentagonal prism is: 5ab + 5bh = (5 × 5 × 4) + (5 × 4 × 6) = 100 + 120
= 220 square feet
The volume of the pentagonal prism is: 5/2 × abh = 5/2 × 5 × 4 × 6 = 300 cubic feet
- A regular pentagonal prism has all equal sides.
- The rectangular faces are perpendicular to the pentagonal faces in a right pentagonal prism.
- A pentagonal prism has 7 faces, 10 vertices, and 15 edges.
- The cross-section of a pentagonal prism is a pentagon.
- A pentagonal prism is also called a heptahedron, which is a polyhedron with seven plane faces.
- What is the sum of the number of sides, faces, and vertices of a pentagonal prism?
a) 32 b) 17 c) 20 d) 40
- What is the number of rectangles in a pentagonal prism?
Related Articles on Pentagonal Prism
Check out these interesting articles on the pentagonal prism. Click to know more!
Solved Examples on Pentagonal Prism
Example 1: Jenifer is packing a chocolate box in the shape of a pentagonal prism. She needs wrapping paper to pack it. Determine the surface area of the wrapping paper needed if the dimensions of the box are as follows:
- Apothem length, a = 10 inches
- Base length, b = 20 inches
- Height, h = 15 inches
To determine the surface area of the wrapping paper, we need to determine the surface area of the box. The surface area of the box is 5ab + 5bh = (5 × 10 × 20) + (5 × 20 × 15) = 1000 + 1500 = 2500 square inches.
∴ The surface area of the wrapping paper 2500 square inches.
Example 2: Emily wants to fill a pentagonal prism-shaped container with water. Determine the capacity of the container so that Emily knows how much water is needed. The dimensions of the container are as follows:
- Apothem length, a = 25 feet
- Base length, b = 17 feet
- Height, h = 15 feet
To know the capacity of the container, we need to find the volume of the container. The volume of the pentagonal prism-shaped container is 5/2 × abh = 5/2 × 25 × 17 × 15 =15,937.5 feet3
∴ The capacity of the container is 15,937.5 feet3
FAQs on Pentagonal Prism
What does an Octagonal Prism look like?
An octagonal prism is a three-dimensional solid. It has two opposite and parallel octagon bases and eight rectangular faces.
What is the Definition of a Prism?
A prism is a 3-dimensional shape with two identical shapes facing each other. These identical shapes are called “bases”, which can be a square, triangle or any polygon. The other faces of a prism are usually parallelograms and rectangles.
What is a 3-D Pentagon called?
A three-dimensional shape that includes pentagons is a pentagonal prism. It includes 2 pentagonal bases and 5 rectangular faces.
What is the Formula for the Surface Area of a Pentagonal Prism?
The surface area of a pentagonal prism can be found out using the following formula: A = 5ab + 5bh.
What is the Formula for the Volume of a Pentagonal Prism?
The volume of a pentagonal prism can be calculated using the following formula: V = 5/2 × a × b × h.
How many Vertices does a Pentagonal Prism have?
There are ten vertices in a pentagonal prism, at both the pentagonal bases of the figure. 5 vertices are there on the top face and five vertices are there on the bottom face.
Is a Cylinder a Prism?
A prism is a polyhedron that has only flat faces. But a cylinder has curved surfaces, therefore, it is not a prism.