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Prisms are three dimensional figures that occupy space. They come in many shapes and sizes and are named by the shape of their base. Prisms have the following characteristics:
- A prism has two congruent bases that are parallel.
- No curves
- Prisms are named by the shape of the base. For example a prism with a triangle base is a triangular prism.
- The base of a prism can be any two parallel sides. If the shape does not have two parallel sides it is not a prism.
- Volume of a prism equals Base Area x Height
- A prism is a polyhedron, which is a solid with faces that are flat
What is a Prism ?
Transcripts
Basics of Prisms
Hi Welcome to MooMooMath. Today we are going to talk about the basics of prisms. The definition of a prism is a three dimensional polygon that has two parallel bases, and they are named by the shape of the bases. So let’s look at our pictures and see which ones have parallel bases. This one has a hexagonal base (6 sides) and it is parallel to this base so it is a hexagonal prism. Let’s look at the prism in the center. It has a base here (points to the top) and a base here (points to the bottom base) so this one is also a prism and this one is a triangular prism. This one over here (points to prism on the top right) we don’t have parallel bases we actually have a circle for our base so this one is not a prism it is a cone. Let’s look at the one lower left. Do we have a base, yes we do and it is a rectangular prism, and the last one does it have a base parallel? No it doesn’t so it is not a prism. So the definition of a prism is a three dimensional figure that has two parallel bases and it is named by the shape of the base. So this one is a square and this one is hexagonal because it has two parallel hexagons. Hope this video was helpful.
The edge is where the two faces intersect
Triangular Prism
Find the surface area of a rectangular prism with a length of 6 units, a height of 3 units and a width of 4 units.
Step 1. Plug in the appropriate units in the formula
2* (6*4) + 2(6*3) + 2( 3*4)
(L*W) ( L*H) (H*W)
Step 2. 2*24 + 2*18 + 2*12
Step 3. 48+36+24 = 108 units squared (surface area is always squared)
How to find the surface area of a prism
The video works the sample area of a prism problem below.
The face is the flat surface of the prism
The base of a prism can be any two parallel sides.
The formula for finding the surface area of a rectangular prism equals:
2* (length *width) + 2(length*height) + 2*(height * width) = surface area of a prism
How do you find the surface area of a prism that is not rectangular?
Surface Area = Lateral Area + 2 Base Areas
The formula for finding the surface area of a non- rectangular prism equals:
The formula for finding the base area will vary according to the shape of the prism.
Check here for a list of base area formulas
Find the surface area of a triangular prism with dimensions 16,12,10, and 20 cm. ( see picture)
Lateral Area = P * h
P = perimeter h = height of prism
Step 1. Find your lateral area. using P * h
P = 16 + 20 + 12 = 48
Multiply 48 x the prism height = 48 * 10 = 480 LA
Step 2. Find your base area. The base is a triangular base therefore use 1/2 base * height 1/2 (12) * 16 = 6 * 16 = 96 base area
You have two bases therefore multiply by 2 2 * 96 = 192
Step 3. Add your lateral area and your base area for the total surface area
480 + 192 = 672 square centimeters