Direct Variation and Cubes

Oct 13, 2025 by wbrum.org 133 views

Introduction

In mathematics, direct variation is a relationship between two variables where one variable is a constant multiple of the other. This relationship can be expressed as y = kx, where y is the dependent variable, x is the independent variable, and k is the constant of variation. In this article, we will explore the concept of direct variation and its application to cubes.

Direct Variation and Cubes

When the cube of y varies directly as z, it means that y^3 = kz, where k is the constant of variation. This relationship can be expressed as:

y^3 = kz

In this equation, y is the dependent variable, z is the independent variable, and k is the constant of variation.

Example: Finding the Value of k

When y = 8, z = 8. We can substitute these values into the equation y^3 = kz to find the value of k.

8^3 = k(8) 512 = 8k k = 64

Now that we have found the value of k, we can use it to find the value of y when z = 64.

Heather's Work

Heather's work in finding the value of y when z = 64 is shown below:

y^3 = k z y^3 = 64(64) y^3 = 4096 y = ∛4096 y = 16

Discussion

Heather's work is correct. The value of y when z = 64 is indeed 16.

Conclusion

In this article, we explored the concept of direct variation and its application to cubes. We found the value of k when y = 8, z = 8, and used it to find the value of y when z = 64. Heather's work in finding the value of y when z = 64 was correct.

Key Takeaways

Direct variation is a relationship between two variables where one variable is a constant multiple of the other.
When the cube of y varies directly as z, it means that y^3 = kz, where k is the constant of variation.
The value of k can be found by substituting the values of y and z into the equation y^3 = kz.
The value of y can be found by substituting the value of z and k into the equation y^3 = kz.

Practice Problems

When y = 12, z = 12. Find the value of k.
When z = 100, find the value of y if k = 2.
When y = 20, z = 20. Find the value of k.
When z = 200, find the value of y if k = 3.
When y = 15, z = 15. Find the value of k.

Solutions

k = 12^3 / 12 = 12^2 = 144
y = ∛(2(100)) = ∛200 = 5.848
k = 20^3 / 20 = 20^2 = 400
y = ∛(3(200)) = ∛600 = 8.165
k = 15^3 / 15 = 15^2 = 225

Conclusion

Introduction

In our previous article, we explored the concept of direct variation and its application to cubes. We discussed how to find the value of k when y = 8, z = 8, and used it to find the value of y when z = 64. In this article, we will provide a Q&A guide to help readers understand the concept of direct variation and its application to cubes.

Q&A

Q: What is direct variation?

A: Direct variation is a relationship between two variables where one variable is a constant multiple of the other. This relationship can be expressed as y = kx, where y is the dependent variable, x is the independent variable, and k is the constant of variation.

Q: What is the equation for direct variation when the cube of y varies directly as z?

A: The equation for direct variation when the cube of y varies directly as z is y^3 = kz, where k is the constant of variation.

Q: How do I find the value of k?

A: To find the value of k, you can substitute the values of y and z into the equation y^3 = kz. For example, if y = 8 and z = 8, you can substitute these values into the equation to find the value of k.

Q: How do I find the value of y when z = 64?

A: To find the value of y when z = 64, you can substitute the value of z and k into the equation y^3 = kz. For example, if z = 64 and k = 64, you can substitute these values into the equation to find the value of y.

Q: What is the value of y when z = 64?

A: The value of y when z = 64 is 16.

Q: How do I find the value of k when y = 12, z = 12?

A: To find the value of k when y = 12, z = 12, you can substitute the values of y and z into the equation y^3 = kz. For example, if y = 12 and z = 12, you can substitute these values into the equation to find the value of k.

Q: What is the value of k when y = 12, z = 12?

A: The value of k when y = 12, z = 12 is 12^2 = 144.

Q: How do I find the value of y when z = 100 and k = 2?

A: To find the value of y when z = 100 and k = 2, you can substitute the values of z and k into the equation y^3 = kz. For example, if z = 100 and k = 2, you can substitute these values into the equation to find the value of y.

Q: What is the value of y when z = 100 and k = 2?

A: The value of y when z = 100 and k = 2 is ∛(2(100)) = ∛200 = 5.848.

Q: How do I find the value of k when y = 20, z = 20?

A: To find the value of k when y = 20, z = 20, you can substitute the values of y and z into the equation y^3 = kz. For example, if y = 20 and z = 20, you can substitute these values into the equation to find the value of k.

Q: What is the value of k when y = 20, z = 20?

A: The value of k when y = 20, z = 20 is 20^2 = 400.

Q: How do I find the value of y when z = 200 and k = 3?

A: To find the value of y when z = 200 and k = 3, you can substitute the values of z and k into the equation y^3 = kz. For example, if z = 200 and k = 3, you can substitute these values into the equation to find the value of y.

Q: What is the value of y when z = 200 and k = 3?

A: The value of y when z = 200 and k = 3 is ∛(3(200)) = ∛600 = 8.165.

Q: How do I find the value of k when y = 15, z = 15?

A: To find the value of k when y = 15, z = 15, you can substitute the values of y and z into the equation y^3 = kz. For example, if y = 15 and z = 15, you can substitute these values into the equation to find the value of k.

Q: What is the value of k when y = 15, z = 15?

A: The value of k when y = 15, z = 15 is 15^2 = 225.

Conclusion

In this Q&A guide, we provided answers to common questions about direct variation and its application to cubes. We hope that this guide has helped readers understand the concept of direct variation and its application to cubes. If you have any further questions, please don't hesitate to ask.

Practice Problems

When y = 18, z = 18. Find the value of k.
When z = 72, find the value of y if k = 3.
When y = 25, z = 25. Find the value of k.
When z = 250, find the value of y if k = 4.
When y = 22, z = 22. Find the value of k.

Solutions

k = 18^3 / 18 = 18^2 = 324
y = ∛(3(72)) = ∛216 = 6
k = 25^3 / 25 = 25^2 = 625
y = ∛(4(250)) = ∛1000 = 10
k = 22^3 / 22 = 22^2 = 484