Math Problem Statement

find the area of the rectangle perimeter is 130 length is (3x-15) width (x-8) find the area

Solution

To find the area of the rectangle, we need to first determine the values of the length and width using the given information, and then calculate the area.

Step 1: Set up the equation for perimeter

The perimeter PP of a rectangle is given by the formula:

P=2(Length+Width)P = 2(\text{Length} + \text{Width})

We are told that the perimeter is 130, the length is 3x153x - 15, and the width is x8x - 8. Substituting these values into the formula:

130=2((3x15)+(x8))130 = 2\left((3x - 15) + (x - 8)\right)

Step 2: Solve for xx

Simplify the equation:

130=2(4x23)130 = 2\left(4x - 23\right)

Divide both sides by 2:

65=4x2365 = 4x - 23

Add 23 to both sides:

88=4x88 = 4x

Now, divide by 4:

x=22x = 22

Step 3: Find the length and width

Now that we have x=22x = 22, we can substitute this value back into the expressions for the length and width:

Length=3x15=3(22)15=6615=51\text{Length} = 3x - 15 = 3(22) - 15 = 66 - 15 = 51

Width=x8=228=14\text{Width} = x - 8 = 22 - 8 = 14

Step 4: Calculate the area

The area AA of a rectangle is given by the formula:

A=Length×WidthA = \text{Length} \times \text{Width}

Substitute the values for the length and width:

A=51×14=714A = 51 \times 14 = 714

So, the area of the rectangle is 714square units714 \, \text{square units}.

Would you like further details or clarification? Here are some related questions:

  1. What if the perimeter was different? How would it change the area?
  2. How does changing xx affect the length and width of the rectangle?
  3. What is the effect on the perimeter when length or width is doubled?
  4. Can we express the area as a function of xx before solving for xx?
  5. How would the problem change if we knew the area but not the perimeter?

Tip: Always check if you need to solve for variables first when working with formulas.

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Math Problem Analysis

Mathematical Concepts

Algebra
Geometry
Rectangles
Linear Equations

Formulas

Perimeter of a rectangle: P = 2(Length + Width)
Area of a rectangle: A = Length × Width

Theorems

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Suitable Grade Level

Grades 7-9