Math Problem Statement

You are planning to make an open rectangular box from a 23-in.-by-45-in. piece of cardboard by cutting congruent squares from the corners and folding up the sides. What are the dimensions of the box of largest volume you can make this way, and what is its volume?

Solution

To solve this problem, let’s go through each step systematically.

  1. Define the Problem: We have a 23-inch by 45-inch piece of cardboard, and we're cutting congruent squares from each corner. Let's call the side length of each square xx. After cutting, we fold up the sides to form an open-top box.

  2. Determine Box Dimensions:

    • After cutting squares of side length xx from each corner:
      • The length of the box will be 452x45 - 2x.
      • The width of the box will be 232x23 - 2x.
      • The height of the box will be xx.
  3. Set Up the Volume Function: The volume VV of a box is given by: V=length×width×heightV = \text{length} \times \text{width} \times \text{height} Substituting in our expressions for length, width, and height: V(x)=(452x)(232x)xV(x) = (45 - 2x)(23 - 2x)x Expanding this equation will give a polynomial in terms of xx, which represents the volume as a function of xx.

  4. Maximize the Volume: To find the maximum volume, we need to find the critical points of V(x)V(x) by differentiating and setting the derivative equal to zero: V(x)=0V'(x) = 0 Then, we’ll evaluate V(x)V(x) at those critical points and within the feasible domain for xx, which is determined by the constraints 0<x<11.50 < x < 11.5 (since cutting squares larger than half the width or length would result in negative dimensions).

  5. Calculate the Optimal Dimensions: Solving for xx will give us the optimal height. Substitute this xx back into the expressions for length and width to obtain the final dimensions of the box with maximum volume.

  6. Compute the Volume: With the optimal xx, we substitute back into V(x)V(x) to find the maximum volume.

Let me calculate this step-by-step.The optimal dimensions of the box with maximum volume are as follows:

  • Length: 35.32 inches
  • Width: 13.32 inches
  • Height: 4.84 inches

The maximum volume of this box is approximately 2277.042277.04 cubic inches.

Would you like further details on any part of the solution, or have any questions?

Here are some related questions for further exploration:

  1. What would happen to the maximum volume if the dimensions of the cardboard changed?
  2. How does changing the height xx affect the dimensions and volume of the box?
  3. Could a different shape (like a square base) achieve a larger volume with the same cardboard?
  4. What if the box needed a lid; how would that change the dimensions for maximum volume?
  5. Is there a way to generalize this solution for any rectangular piece of cardboard?

Tip: For similar problems, always start by defining variables and writing equations based on the problem’s constraints. This approach simplifies finding optimal values.

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Math Problem Analysis

Mathematical Concepts

Optimization
Volume of Rectangular Prism
Polynomials
Critical Points

Formulas

Volume of a box: V = length × width × height
Dimensions after cutting squares: length = 45 - 2x, width = 23 - 2x, height = x
Volume function for the box: V(x) = (45 - 2x)(23 - 2x)x

Theorems

Maximization of polynomial functions using critical points

Suitable Grade Level

Grades 10-12