October 14, 2022

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

A prism is a crucial shape in geometry. The shape’s name is originated from the fact that it is made by considering a polygonal base and expanding its sides until it cross the opposite base.

This blog post will talk about what a prism is, its definition, different types, and the formulas for surface areas and volumes. We will also give instances of how to employ the data given.

What Is a Prism?

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

Definition

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

  1. A lateral face (meaning both height AND depth)

  2. Two parallel planes which make up each base

  3. An illusory line standing upright across any provided point on either side of this figure's core/midline—also known collectively as an axis of symmetry

  4. Two vertices (the plural of vertex) where any three planes meet





Kinds 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 sides that are all rectangles. It looks like 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 makes it apart.

The Formula for the Volume of a Prism

Volume is a measurement of the sum of area that an object occupies. As an essential figure in geometry, the volume of a prism is very important for your learning.

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

V = Volume

B = Base area

h= Height

Finally, given that bases can have all kinds of shapes, you have to retain few formulas to calculate the surface area of the base. Still, we will go through that later.

The Derivation of the Formula

To derive the formula for the volume of a rectangular prism, we are required to look at a cube. A cube is a 3D item 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 get 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 stands for the base area of the rectangle. The h in the formula stands for height, that is how dense 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 Utilize the Formula

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

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 work on another problem, let’s work on 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 have the surface area and height, you will calculate the volume with no problem.

The Surface Area of a Prism

Now, let’s talk regarding the surface area. The surface area of an item is the measure of the total area that the object’s surface comprises of. It is an important part of the formula; therefore, we must learn how to find it.

There are a several different ways to figure out the surface area of a prism. To measure the surface area of a rectangular prism, you can use 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 work out the surface area of a triangular prism, we will utilize this formula:

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

assuming,

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 Calculating the Surface Area of a Rectangular Prism

Initially, we will work on the total surface area of a rectangular prism with the following dimensions.

l=8 in

b=5 in

h=7 in

To solve 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 Calculating the Surface Area of a Triangular Prism

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

This prism will have 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 information, you should be able to calculate any prism’s volume and surface area. Check out for yourself and see how easy it is!

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