# Volume of a Prism - Formula, Derivation, Definition, Examples

A prism is a vital figure in geometry. The shape’s name is originated from the fact that it is made by taking a polygonal base and stretching its sides as far as it intersects the opposing base.

This article post will discuss what a prism is, its definition, different kinds, and the formulas for surface areas and volumes. We will also provide instances of how to employ the data provided.

## What Is a Prism?

A prism is a 3D geometric shape with two congruent and parallel faces, well-known as bases, that take the form of a plane figure. The other faces are rectangles, and their count depends on how many sides the identical base has. For example, if the bases are triangular, the prism would have three sides. If the bases are pentagons, there will be five sides.

### Definition

The characteristics of a prism are fascinating. The base and top each have an edge in common with the additional two sides, creating them congruent to one another as well! This states that every three dimensions - length and width in front and depth to the back - can be deconstructed into these four entities:

A lateral face (meaning both height AND depth)

Two parallel planes which constitute of each base

An fictitious line standing upright through any provided point on any side of this figure's core/midline—known collectively as an axis of symmetry

Two vertices (the plural of vertex) where any three planes join

### Types of Prisms

There are three main kinds of prisms:

Rectangular prism

Triangular prism

Pentagonal prism

The rectangular prism is a regular kind of prism. It has six faces that are all rectangles. It matches the looks of a box.

The triangular prism has two triangular bases and three rectangular faces.

The pentagonal prism comprises of two pentagonal bases and five rectangular faces. It looks a lot like a triangular prism, but the pentagonal shape of the base stands out.

## The Formula for the Volume of a Prism

Volume is a measurement of the sum of area that an item occupies. As an essential shape in geometry, the volume of a prism is very relevant in your learning.

The formula for the volume of a rectangular prism is V=B*h, where,

V = Volume

B = Base area

h= Height

Consequently, considering bases can have all types of shapes, you will need to know a few formulas to calculate the surface area of the base. However, we will touch upon that later.

### The Derivation of the Formula

To derive the formula for the volume of a rectangular prism, we have to observe a cube. A cube is a three-dimensional item with six sides that are all squares. The formula for the volume of a cube is V=s^3, assuming,

V = Volume

s = Side length

Now, we will take a slice out of our cube that is h units thick. This slice will by itself be a rectangular prism. The volume of this rectangular prism is B*h. The B in the formula stands for the base area of the rectangle. The h in the formula refers to height, that is how thick our slice was.

Now that we have a formula for the volume of a rectangular prism, we can use it on any type of prism.

### Examples of How to Use the Formula

Considering we have the formulas for the volume of a pentagonal prism, triangular prism, and rectangular prism, now let’s use them.

First, let’s work on the volume of a rectangular prism with a base area of 36 square inches and a height of 12 inches.

V=B*h

V=36*12

V=432 square inches

Now, let’s try one more problem, let’s calculate the volume of a triangular prism with a base area of 30 square inches and a height of 15 inches.

V=Bh

V=30*15

V=450 cubic inches

Considering that you possess the surface area and height, you will figure out the volume with no problem.

## The Surface Area of a Prism

Now, let’s discuss about the surface area. The surface area of an object is the measure of the total area that the object’s surface consist of. It is an essential part of the formula; thus, we must understand how to find it.

There are a several distinctive ways to figure out the surface area of a prism. To figure out the surface area of a rectangular prism, you can utilize this: A=2(lb + bh + lh), where,

l = Length of the rectangular prism

b = Breadth of the rectangular prism

h = Height of the rectangular prism

To figure out the surface area of a triangular prism, we will utilize this formula:

SA=(S1+S2+S3)L+bh

where,

b = The bottom edge of the base triangle,

h = height of said triangle,

l = length of the prism

S1, S2, and S3 = The three sides of the base triangle

bh = the total area of the two triangles, or [2 × (1/2 × bh)] = bh

We can also utilize SA = (Perimeter of the base × Length of the prism) + (2 × Base area)

### Example for Computing the Surface Area of a Rectangular Prism

Initially, we will determine the total surface area of a rectangular prism with the following data.

l=8 in

b=5 in

h=7 in

To calculate this, we will replace these numbers into the respective formula as follows:

SA = 2(lb + bh + lh)

SA = 2(8*5 + 5*7 + 8*7)

SA = 2(40 + 35 + 56)

SA = 2 × 131

SA = 262 square inches

### Example for Finding the Surface Area of a Triangular Prism

To calculate the surface area of a triangular prism, we will work on the total surface area by following similar steps as before.

This prism consists of a base area of 60 square inches, a base perimeter of 40 inches, and a length of 7 inches. Hence,

SA=(Perimeter of the base × Length of the prism) + (2 × Base Area)

Or,

SA = (40*7) + (2*60)

SA = 400 square inches

With this data, you should be able to figure out any prism’s volume and surface area. Test it out for yourself and observe how easy it is!

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