Math Problem Statement

Find the length and width of a rectangle that has the given perimeter and a maximum area. Perimeter: 64 meters.

Solution

The problem asks to find the dimensions (length and width) of a rectangle that has a perimeter of 64 meters and a maximum area.

Steps:

  1. Perimeter Formula: The perimeter PP of a rectangle is given by: P=2L+2WP = 2L + 2W where LL is the length and WW is the width.

    Given that the perimeter is 64 meters: 64=2L+2WorL+W=3264 = 2L + 2W \quad \text{or} \quad L + W = 32

  2. Maximizing Area: The area AA of a rectangle is given by: A=L×WA = L \times W To maximize the area, we use the relationship L+W=32L + W = 32. Solve for one variable in terms of the other. Let’s solve for LL: L=32WL = 32 - W

    Substitute this into the area equation: A=(32W)×W=32WW2A = (32 - W) \times W = 32W - W^2 This is a quadratic equation in terms of WW, and it represents a parabola that opens downward. The maximum area occurs at the vertex of the parabola, which is found by the formula: W=b2aW = \frac{-b}{2a} where a=1a = -1 and b=32b = 32. So: W=322(1)=16W = \frac{-32}{2(-1)} = 16

  3. Finding LL: Since L+W=32L + W = 32 and W=16W = 16: L=3216=16L = 32 - 16 = 16

Conclusion:

The length and width that give a maximum area for the rectangle are both 16 meters, meaning the rectangle is actually a square.

Would you like further details or have any other questions?

Related Questions:

  1. How do you find the perimeter of a rectangle given the area?
  2. What are the steps for solving optimization problems in calculus?
  3. Why is the area maximized when the rectangle is a square?
  4. How can you verify the maximum area using derivatives?
  5. What is the difference between maximizing and minimizing functions in geometry?

Tip:

For rectangles, a square always gives the maximum area when the perimeter is fixed!

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Math Problem Analysis

Mathematical Concepts

Geometry
Optimization
Quadratic Equations

Formulas

Perimeter of a rectangle: P = 2L + 2W
Area of a rectangle: A = L × W
Quadratic equation for area: A = 32W - W^2
Formula to find vertex of quadratic equation: W = -b / 2a

Theorems

Maximum area of a rectangle with fixed perimeter occurs when it is a square

Suitable Grade Level

Grades 8-10