Formula for Surface Area of a Rectangular Prism

Oct 13, 2025 by wbrum.org 149 views

Introduction

In geometry, a rectangular prism is a three-dimensional shape with six rectangular faces. It has three dimensions: length, width, and height. The surface area of a rectangular prism is the sum of the areas of all its faces. In this article, we will discuss how to find the missing width of a rectangular prism given its length, height, and surface area.

Formula for Surface Area of a Rectangular Prism

The surface area (SA) of a rectangular prism is given by the formula:

SA = 2lw + 2lh + 2wh

where l is the length, w is the width, and h is the height.

Given Values

We are given the following values:

Length (l) = 6 cm
Height (h) = 4 cm
Surface Area (SA) = 188 cm²

Finding the Missing Width

We need to find the missing width (w). To do this, we can substitute the given values into the formula for surface area and solve for w.

SA = 2lw + 2lh + 2wh 188 = 2(6)w + 2(6)(4) + 2w(4) 188 = 12w + 48 + 8w 188 = 20w + 48

Solving for w

Now, we can solve for w by subtracting 48 from both sides and then dividing by 20.

188 - 48 = 20w 140 = 20w w = 140/20 w = 7

Conclusion

The missing width of the rectangular prism is 7 cm.

Example Use Case

This problem can be used to teach students how to find the missing dimension of a rectangular prism given its surface area and other dimensions. It can also be used to practice solving equations and formulas in geometry.

Real-World Application

In real-world applications, finding the missing width of a rectangular prism can be useful in various fields such as architecture, engineering, and design. For example, in building design, architects need to calculate the surface area of a building to determine the amount of materials needed for construction. In this case, finding the missing width of a rectangular prism can help them determine the correct dimensions of the building.

Tips and Tricks

When solving equations, make sure to isolate the variable by adding, subtracting, multiplying, or dividing both sides of the equation by the same value.
Use formulas and equations to solve problems in geometry.
Practice solving equations and formulas to become proficient in geometry.

Frequently Asked Questions

Q: What is the formula for surface area of a rectangular prism? A: The formula for surface area of a rectangular prism is SA = 2lw + 2lh + 2wh.
Q: How do I find the missing width of a rectangular prism? A: To find the missing width, substitute the given values into the formula for surface area and solve for w.
Q: What is the missing width of a rectangular prism with a length of 6 cm, a height of 4 cm, and a surface area of 188 cm²? A: The missing width of the rectangular prism is 7 cm.

Introduction

In our previous article, we discussed how to find the missing width of a rectangular prism given its length, height, and surface area. In this article, we will provide a comprehensive Q&A section to address common questions and concerns related to rectangular prisms.

Q&A Section

Q: What is a rectangular prism?

A: A rectangular prism is a three-dimensional shape with six rectangular faces. It has three dimensions: length, width, and height.

Q: What is the formula for surface area of a rectangular prism?

A: The formula for surface area of a rectangular prism is SA = 2lw + 2lh + 2wh, where l is the length, w is the width, and h is the height.

Q: How do I find the missing width of a rectangular prism?

A: To find the missing width, substitute the given values into the formula for surface area and solve for w.

Q: What is the missing width of a rectangular prism with a length of 6 cm, a height of 4 cm, and a surface area of 188 cm²?

A: The missing width of the rectangular prism is 7 cm.

Q: Can I use the formula for surface area to find the missing length or height of a rectangular prism?

A: Yes, you can use the formula for surface area to find the missing length or height of a rectangular prism by rearranging the formula and solving for the unknown dimension.

Q: How do I calculate the volume of a rectangular prism?

A: To calculate the volume of a rectangular prism, multiply the length, width, and height together: V = lwh.

Q: What is the difference between a rectangular prism and a cube?

A: A rectangular prism is a three-dimensional shape with six rectangular faces, while a cube is a three-dimensional shape with six square faces.

Q: Can I use the formula for surface area to find the missing dimension of a cube?

A: Yes, you can use the formula for surface area to find the missing dimension of a cube by rearranging the formula and solving for the unknown dimension.

Q: How do I find the missing dimension of a rectangular prism with a surface area of 120 cm² and a length of 5 cm?

A: To find the missing dimension, substitute the given values into the formula for surface area and solve for the unknown dimension.

Q: What is the missing dimension of a rectangular prism with a surface area of 120 cm² and a length of 5 cm?

A: To find the missing dimension, we need to know the height of the prism. Let's assume the height is h. Then, we can substitute the given values into the formula for surface area and solve for h.

120 = 2(5)h + 2(5)(h) + 2h(5) 120 = 10h + 10h + 10h 120 = 30h h = 120/30 h = 4

Now that we know the height, we can find the missing width by substituting the values into the formula for surface area and solving for w.

120 = 2(5)w + 2(5)(4) + 2w(4) 120 = 10w + 40 + 8w 120 = 18w + 40 80 = 18w w = 80/18 w = 4.44

Q: Can I use the formula for surface area to find the missing dimension of a rectangular prism with a surface area of 240 cm² and a length of 8 cm?

A: Yes, you can use the formula for surface area to find the missing dimension of a rectangular prism with a surface area of 240 cm² and a length of 8 cm.

240 = 2(8)w + 2(8)(h) + 2w(8) 240 = 16w + 16h + 16w 240 = 32w + 16h

Now that we know the surface area and the length, we can find the missing width and height by substituting the values into the formula for surface area and solving for w and h.

Q: What is the missing dimension of a rectangular prism with a surface area of 240 cm² and a length of 8 cm?

A: To find the missing dimension, we need to know the height of the prism. Let's assume the height is h. Then, we can substitute the given values into the formula for surface area and solve for h.

240 = 32w + 16h 240 = 32(8) + 16h 240 = 256 + 16h -16 = 16h h = -16/16 h = -1

Now that we know the height, we can find the missing width by substituting the values into the formula for surface area and solving for w.

240 = 32w + 16(-1) 240 = 32w - 16 256 = 32w w = 256/32 w = 8

Conclusion

In this Q&A section, we have addressed common questions and concerns related to rectangular prisms. We have provided formulas and examples to help you find the missing width, length, and height of a rectangular prism. We have also discussed how to calculate the volume of a rectangular prism and the difference between a rectangular prism and a cube.