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

A prism is a vital shape in geometry. The figure’s name is derived from the fact that it is created by taking a polygonal base and expanding its sides as far as it cross the opposing base.

This article post will talk about what a prism is, its definition, different kinds, and the formulas for surface areas and volumes. We will also offer instances of how to utilize the information given.

## What Is a Prism?

A prism is a three-dimensional geometric figure with two congruent and parallel faces, called bases, which take the shape of a plane figure. The other faces are rectangles, and their count depends on how many sides the similar base has. For example, if the bases are triangular, the prism would have three sides. If the bases are pentagons, there would be five sides.

### Definition

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

A lateral face (meaning both height AND depth)

Two parallel planes which make up each base

An fictitious line standing upright across any provided point on any side of this shape'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 major types of prisms:

Rectangular prism

Triangular prism

Pentagonal prism

The rectangular prism is a common kind of prism. It has six faces that are all rectangles. It looks like a box.

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

The pentagonal prism consists of two pentagonal bases and five rectangular faces. It seems almost like a triangular prism, but the pentagonal shape of the base sets it apart.

## The Formula for the Volume of a Prism

Volume is a measure of the total amount of space that an thing occupies. As an crucial figure in geometry, the volume of a prism is very important for your studies.

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

V = Volume

B = Base area

h= Height

Consequently, since bases can have all sorts of figures, you are required to retain few formulas to calculate the surface area of the base. However, we will go through that later.

### The Derivation of the Formula

To extract the formula for the volume of a rectangular prism, we are required to look at a cube. A cube is a three-dimensional object with six sides that are all squares. The formula for the volume of a cube is V=s^3, where,

V = Volume

s = Side length

Now, we will have a slice out of our cube that is h units thick. This slice will make a rectangular prism. The volume of this rectangular prism is B*h. The B in the formula implies the base area of the rectangle. The h in the formula refers to height, that is how dense our slice was.

Now that we have a formula for the volume of a rectangular prism, we can generalize it to any kind of prism.

### Examples of How to Utilize the Formula

Since we understand the formulas for the volume of a pentagonal prism, triangular prism, and rectangular prism, let’s utilize these now.

First, let’s figure out 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 another problem, let’s figure out 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 work out the volume without any issue.

## The Surface Area of a Prism

Now, let’s talk regarding the surface area. The surface area of an object is the measurement of the total area that the object’s surface occupies. It is an crucial part of the formula; therefore, we must know how to find it.

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

l = Length of the rectangular prism

b = Breadth of the rectangular prism

h = Height of the rectangular prism

To compute 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 use SA = (Perimeter of the base × Length of the prism) + (2 × Base area)

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

First, we will figure out the total surface area of a rectangular prism with the ensuing dimensions.

l=8 in

b=5 in

h=7 in

To solve this, we will replace these values 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 find the surface area of a triangular prism, we will figure out the total surface area by following same 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. Thus,

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

Or,

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

SA = 400 square inches

With this knowledge, you will be able to compute any prism’s volume and surface area. Check out for yourself and see how easy it is!

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