Expressing the Perimeter in Terms of the Width

Oct 13, 2025 by wbrum.org 87 views

The Length of a Rectangle and Its Perimeter: Modeling the Relationship

In geometry, the perimeter of a rectangle is the sum of the lengths of all its sides. Given that the length of a rectangle is four times its width, we can express the perimeter as a function of the width. In this article, we will explore the relationship between the width and the perimeter of the rectangle, and derive an inequality that models this relationship.

Let's denote the width of the rectangle as $w$ . Since the length of the rectangle is four times its width, the length can be expressed as $4w$ . The perimeter of the rectangle is the sum of all its sides, which is given by the formula:

P = 2l + 2w

where $P$ is the perimeter, $l$ is the length, and $w$ is the width.

Expressing the Perimeter in Terms of the Width

Substituting the expression for the length ( $4w$ ) into the formula for the perimeter, we get:

P = 2(4w) + 2w

Simplifying the expression, we get:

P = 8w + 2w

P = 10w

Modeling the Relationship between the Width and the Perimeter

We are given that the perimeter of the rectangle is at most 130 cm. This can be expressed as an inequality:

P \leq 130

Substituting the expression for the perimeter in terms of the width ( $10w$ ), we get:

10w \leq 130

Solving the Inequality

To solve the inequality, we can divide both sides by 10:

w \leq \frac{130}{10}

w \leq 13

In conclusion, the inequality that models the relationship between the width and the perimeter of the rectangle is:

w \leq 13

This inequality states that the width of the rectangle is at most 13 cm, given that the perimeter of the rectangle is at most 130 cm.

The inequality $w \leq 13$ can be interpreted as follows:

If the width of the rectangle is 13 cm, the perimeter of the rectangle is 130 cm.
If the width of the rectangle is less than 13 cm, the perimeter of the rectangle is less than 130 cm.

This inequality provides a useful constraint on the possible values of the width of the rectangle, given a fixed perimeter.

Suppose we want to find the maximum width of a rectangle with a perimeter of 120 cm. We can use the inequality $w \leq 13$ to find the maximum width:

w \leq 13

Since the perimeter is 120 cm, which is less than 130 cm, the maximum width of the rectangle is still 13 cm.

The inequality $w \leq 13$ has several applications in real-world problems, such as:

Designing rectangular buildings with a fixed perimeter.
Creating rectangular packages with a fixed perimeter.
Modeling the relationship between the width and the perimeter of a rectangle in a variety of contexts.

In conclusion, the inequality $w \leq 13$ models the relationship between the width and the perimeter of a rectangle, given that the length of the rectangle is four times its width and the perimeter is at most 130 cm. This inequality provides a useful constraint on the possible values of the width of the rectangle, and has several applications in real-world problems.
The Length of a Rectangle and Its Perimeter: Modeling the Relationship - Q&A

In our previous article, we explored the relationship between the width and the perimeter of a rectangle, given that the length of the rectangle is four times its width. We derived an inequality that models this relationship, which is:

w \leq 13

This inequality states that the width of the rectangle is at most 13 cm, given that the perimeter of the rectangle is at most 130 cm.

Q: What is the relationship between the width and the perimeter of a rectangle?

A: The relationship between the width and the perimeter of a rectangle is given by the inequality $w \leq 13$ , where $w$ is the width of the rectangle and 13 is the maximum width given a perimeter of 130 cm.

Q: How do I use the inequality to find the maximum width of a rectangle with a given perimeter?

A: To find the maximum width of a rectangle with a given perimeter, you can use the inequality $w \leq 13$ . For example, if the perimeter is 120 cm, you can substitute this value into the inequality to find the maximum width:

w \leq \frac{120}{10}

w \leq 12

Q: What if the length of the rectangle is not four times its width? How do I find the relationship between the width and the perimeter?

A: If the length of the rectangle is not four times its width, you can use the formula for the perimeter of a rectangle:

P = 2l + 2w

where $P$ is the perimeter, $l$ is the length, and $w$ is the width. You can then substitute the expression for the length into the formula and simplify to find the relationship between the width and the perimeter.

Q: Can I use the inequality to find the relationship between the length and the perimeter of a rectangle?

A: Yes, you can use the inequality to find the relationship between the length and the perimeter of a rectangle. Since the length is four times the width, you can substitute the expression for the length into the inequality:

4w \leq 13

w \leq \frac{13}{4}

This inequality states that the length of the rectangle is at most 3.25 cm, given that the perimeter of the rectangle is at most 130 cm.

Q: What are some real-world applications of the inequality?

A: The inequality has several real-world applications, such as:

Designing rectangular buildings with a fixed perimeter.
Creating rectangular packages with a fixed perimeter.
Modeling the relationship between the width and the perimeter of a rectangle in a variety of contexts.

Q: What is the relationship between the width and the perimeter of a rectangle? A: The relationship between the width and the perimeter of a rectangle is given by the inequality $w \leq 13$ .
Q: How do I use the inequality to find the maximum width of a rectangle with a given perimeter? A: To find the maximum width of a rectangle with a given perimeter, you can use the inequality $w \leq 13$ .
Q: What if the length of the rectangle is not four times its width? How do I find the relationship between the width and the perimeter? A: If the length of the rectangle is not four times its width, you can use the formula for the perimeter of a rectangle and substitute the expression for the length into the formula.
Q: Can I use the inequality to find the relationship between the length and the perimeter of a rectangle? A: Yes, you can use the inequality to find the relationship between the length and the perimeter of a rectangle.

Geometry Formulas: A list of geometry formulas, including the formula for the perimeter of a rectangle.
Rectangle Properties: A list of properties of rectangles, including the relationship between the width and the perimeter.
Real-World Applications: A list of real-world applications of the inequality, including designing rectangular buildings and creating rectangular packages.