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| 19 Theory slides |
| 13 Exercises - Grade E - A |
| Each lesson is meant to take 1-2 classroom sessions |
Here are a few recommended readings before getting started with this lesson.
Prisms can be categorized by the shape of their bases. For example, a prism with a triangular base is called a triangular prism. A rectangular prism, on the other hand, has a rectangular base.
Determine whether the given solid is a triangular prism, a rectangular prism, or neither.
There are two important characteristics that give information about 3D objects.
The volume of a solid is the measure of the amount of space inside the solid. It is the three-dimensional equivalent of the area of the figure. Volume is measured using cubic units, such as cubic meters, or m^3. The applet below illustrates the volume of some solids. Move the slider to fill the solids.
The surface area SA of a three-dimensional shape is the total area of all the surfaces of the shape. The lateral area LA is the total area of all lateral surfaces, the surfaces of the shape that are not bases. Lateral area can be defined for polyhedrons, cones, and cylinders. In these instances, the surface area of the shape can be calculated by the formula below.
SA=LA+Area of the Bases
The net of a solid can be helpful to visualize the surfaces of a three-dimensional figure.
Consider a prism with a base area B and height h.
The volume of the prism is calculated by multiplying the base's area by its height.
V = Bh
By Cavalieri's principle, this formula holds true for all types of prisms, including skewed ones.
Recall that the volume of a solid is the measure of the amount of space inside the solid. Note that the top and bottom faces of the prism are always the same and parallel to each other.
Additionally, the prism is, so to speak, filled
with identical base areas that are stacked on top of each other to the height of the prism.
This means that the volume of the prism can be calculated as the sum of all these base areas. The number of bases is equal to the height of the prism. Therefore, the volume of a prism equals the product of its base area and height. V=B+B+B+...+B+B_h ⇓ V=B* h
Consider a prism with a height h, base area B, and base perimeter P.
The surface area of the prism is the sum of the two base areas and the lateral area, which can be calculated as the product of the base perimeter and the height of the prism.
SA=2B+Ph
The surface area of the prism can be seen as the sum of two separate parts: the lateral area and the combined area of the two identical bases. Surface Area = Lateral Area+ 2* Base The base area, often symbolized as B, can be substituted into the equation. Surface Area = Lateral Area+ 2B To determine the lateral area of the prism, consider a net of the given prism. Let a be the length of the side of the base, assuming that it is a regular polygon.
Notice that the lateral surface consists of rectangles equal to the number of sides in the base. The pentagonal prism shown here has five lateral faces because a pentagon has five sides. The area of each rectangular lateral face is the product of its sides a and h. One Lateral Face A=ah If there are n rectangular lateral faces in a prism, then the total lateral area is the product of n and the area of one lateral face. Lateral Area nah Notice that na is the perimeter of the base, which is often denoted by P. Then, the lateral area can be expressed as follows. Lateral Area= Ph Therefore, the formula for the surface area is obtained.
ccccc Surface Area & = & Lateral Area & + & 2* Base [0.8em] SA & =& Ph & + & 2B
Note that although this proof is written for a regular prism, it is also true for a non-regular prism.
It is possible to derive two specific formulas for the volume and surface area of a rectangular prism.
Consider a rectangular prism with a width w, length l, and height h.
The volume of the prism is calculated by multiplying the area of the base by the height of the prism.
V = wl h
The volume of a prism can found by multiplying the base area B and height h. V=B* h The base of a rectangular prism is a rectangle. The area of a rectangle is the product of its width w and length l. B=wl Substitute this expression for B in the first formula. V= B* h ⇓ V= wl h This process produces the formula for the volume of a rectangular prism.
Consider a rectangular prism with a height h, base area B, and base perimeter P.
The surface area of the rectangular prism can be found using the following formula.
SA=2(wl+hl+hw)
P= 2(w+l), B= wl
Distribute h
Factor out 2
Consider a cube with a side length s.
The volume V of the cube can be calculated by raising the side length s to the power of 3, or cubing
it.
V=s^3
The volume of a prism is calculated by multiplying the area of one base by the height. For rectangular prisms, this value is found by multiplying the area of the rectangular base by the height of the prism. Volume of aRectangular Prism V= B* h B=l * w ⇒ V=l * w* h A square is a special type of rectangle whose length and width are equal, so the area of a square is found by calculating the square of the side length. Similarly, a cube is a special type of rectangular prism whose length, width, and height are equal.
Consider a cube with a side length s.
The surface area of the cube is given by the following formula.
SA=6s^2
Substitute values
a* a=a^2
Add terms
Substitute values
Multiply
Add terms
Multiply
Find the width of the prism by using the known volume of the prism and the formula for the volume of a rectangular prism. Then, use the formula for the surface area of a rectangular prism.
Substitute values
Multiply
Commutative Property of Multiplication
Rearrange equation
.LHS /2.8.=.RHS /2.8.
Use a calculator
Substitute values
Multiply
Add terms
Multiply
b= 7, h= 2.3
Multiply
1/b* a = a/b
Calculate quotient
Substitute values
Multiply
Add terms
Use the formula for the surface area of a prism and the given surface area to find the height of the prism. Then, find the volume of the prism.
b= 4, h= 2.7
Multiply
1/b* a = a/b
Calculate quotient
Substitute values
Multiply
LHS-10.8=RHS-10.8
Rearrange equation
.LHS /11.5.=.RHS /11.5.
Calculate the volume or surface area of the triangular or rectangular prism given the base area B, the height, and the side length of the base. The base is always a regular polygon. Round the answer to one decimal place if necessary.
Use the general formula for the volume of a prism to calculate the volume of the triangular prism. Then, use the formula for the volume of a rectangular prism to find the volume of the rectangular prism. Compare the volumes.
There are two possible shapes of the dog house for Bubbles. To determine which one offers the most space for the dog, each of their volumes should be calculated.
h= 1, b= 1.2
1* a=a
1/b* a = a/b
Calculate quotient
B= 0.6, h= 2
Multiply
Substitute values
Multiply
Finally, the volumes of the prisms can be compared.
Volume of the Triangular Prism | Volume of the Rectangular Prism |
---|---|
1.2in.^3 | 1.6in.^3 |
The volume of the rectangular prism is greater than the volume of the triangular prism. This means that the dog house in the shape of the rectangular prism is more spacious, so Mark should choose that one.
Match each name to a figure.
We are given four different three-dimensional figures. Let's analyze each of them to determine its name.
Consider the first given figure.
We can see that this figure has a rectangular base and four triangular lateral faces that have a common vertex. This description matches the definition of a pyramid.
Let's take a look at the second given figure.
We can see that the figure has two rectangular parallel bases that are connected by four rectangular lateral faces. This description matches the definition of a rectangular prism.
Let's analyze the third given figure.
This figure has six identical square faces. This information corresponds to the definition of a cube.
Consider the last given figure.
We can see that it has two triangular parallel bases connected by three rectangular lateral faces. This matches the definition of a triangular prism.
Consider a cube with a side length of 7 feet.
We are asked to calculate the volume of a cube. Let's start by recalling that the volume of a cube is calculated by raising the side length to the power of 3. V=s^3 We know that the side length of the cube is 7 feet. Let's substitute this value into the formula and evaluate V.
The volume of the cube is 343 cubic feet.
Consider a cube with a side length of 9 inches.
We are asked to calculate the surface area of the cube. Let's start by recalling the formula for the surface area of a cube. S=6s^2 We know that the side length of the cube is 9 inches. Substitute this value into the formula and evaluate S.
The surface area of the cube is 486 square inches.
Consider a rectangular prism with the given dimensions.
We are asked to find the volume of the given prism. Let's start by recalling that the volume of a rectangular prism is calculated as the product of the width w, the length l, and the height h of the prism. V=wl h From the diagram, we know that the width of the prism is 3 meters, the length is 4 meters, and the height is 5 meters. Let's substitute these values into the formula and evaluate V.
The volume of the prism is 60 cubic meters.
Consider a triangular prism with the given dimensions.
We are asked to find the volume of the given prism. Let's start by recalling that the volume of a prism is calculated as the product of the base area B and the height of the prism h. V=Bh From the diagram, we can see that the base of the prism is a right triangle with a height h of 12 inches and a base b that is 15 inches long. We can calculate its area by using the following formula. A=1/2bh Substitute 15 for b and 12 for h and solve for A.
We found that the base area of the prism is 90 square inches. Now we have enough information to calculate the volume of the prism. Let's substitute 90 for B and 24 for h into the formula for the volume of a prism and evaluate V.
The volume of the prism is 2160 cubic inches.
Consider a rectangular prism with the given dimensions.
We are asked to calculate the surface area of the prism. Let's start by recalling the formula for the surface area of a rectangular prism. S=2(wl+hl+wh) Here, w is the width, l is the length, and h is the height of the prism. From the diagram, we know that the width of the prism is 9 centimeters, the length is 18 centimeters, and the height is 12 centimeters. Let's substitute these values into the formula and evaluate S.
We found that the surface area of the prism is 972 square centimeters.
Consider a triangular prism with the given dimensions.
We are asked to calculate the surface area of the prism. Let's begin by recalling the formula for the surface area of a prism. S=2B+Ph In this formula, B is the area of one base, P is the perimeter of the base, and h is the height of the prism. We can see that the base of the prism is a triangle.
The area of a triangle with a height h and a base length b is calculated as half the product of h and b. A=1/2bh Let's substitute 8 for b and 3 for h into this formula and solve for A.
The area of the triangle — and, consequently, the base area of the prism — is 12 square millimeters. Next,let's calculate the perimeter of the triangle by adding all the side lengths of the triangle together. P=8+5+5=18mm Finally, we will substitute 12 for B, 18 for P, and 10 for h into the formula for the surface area of a prism. Then we can evaluate S. Let's do it!
The surface area of the given triangular prism is 204 square millimeters.