Math Problem Statement

If 1100 square centimeters of material is available to make a box with a square base and an open top, find the largest possible volume of the box.

Solution

To find the largest possible volume of the box with a square base and an open top, we need to use optimization techniques. Here's how we approach it:

Step 1: Define the variables

Let:

  • xx be the length of the side of the square base (in cm),
  • hh be the height of the box (in cm).

Step 2: Write the surface area equation

The surface area AA consists of:

  • The area of the square base: x2x^2,
  • The area of the four sides (each with area xhxh): 4xh4xh.

The total surface area is given by the sum of these areas, and we know that the total surface area is 1100 cm²: x2+4xh=1100.x^2 + 4xh = 1100.

Step 3: Write the volume equation

The volume VV of the box is: V=x2h.V = x^2 h.

Step 4: Solve for hh in terms of xx

From the surface area equation: x2+4xh=1100,x^2 + 4xh = 1100, solve for hh: 4xh=1100x2,4xh = 1100 - x^2, h=1100x24x.h = \frac{1100 - x^2}{4x}.

Step 5: Substitute hh into the volume equation

Now, substitute this expression for hh into the volume equation V=x2hV = x^2 h: V=x2(1100x24x),V = x^2 \left( \frac{1100 - x^2}{4x} \right), V=x(1100x2)4.V = \frac{x(1100 - x^2)}{4}.

Step 6: Simplify the volume equation

Simplify the equation for volume: V=1100xx34.V = \frac{1100x - x^3}{4}.

Step 7: Maximize the volume

To find the maximum volume, we need to differentiate VV with respect to xx, and then set the derivative equal to zero to find the critical points.

First, differentiate: dVdx=11003x24.\frac{dV}{dx} = \frac{1100 - 3x^2}{4}.

Set dVdx=0\frac{dV}{dx} = 0 to find critical points: 11003x2=0,1100 - 3x^2 = 0, 3x2=1100,3x^2 = 1100, x2=11003,x^2 = \frac{1100}{3}, x=1100319.17cm.x = \sqrt{\frac{1100}{3}} \approx 19.17 \, \text{cm}.

Step 8: Verify if this gives a maximum

To verify if this is a maximum, we check the second derivative: d2Vdx2=6x4=3x2.\frac{d^2V}{dx^2} = -\frac{6x}{4} = -\frac{3x}{2}. Since x>0x > 0, d2Vdx2<0\frac{d^2V}{dx^2} < 0, confirming that this critical point corresponds to a maximum.

Step 9: Calculate the maximum volume

Now, substitute x=19.17x = 19.17 cm into the equation for hh: h=1100(19.17)24(19.17)1100367.576.68732.576.689.55cm.h = \frac{1100 - (19.17)^2}{4(19.17)} \approx \frac{1100 - 367.5}{76.68} \approx \frac{732.5}{76.68} \approx 9.55 \, \text{cm}.

Finally, the maximum volume is: V=x2h=(19.17)2×9.55367.5×9.553503.63cm3.V = x^2 h = (19.17)^2 \times 9.55 \approx 367.5 \times 9.55 \approx 3503.63 \, \text{cm}^3.

Final Answer:

The largest possible volume of the box is approximately 3503.63 cubic centimeters.

Would you like further details on the solution or have any specific questions?


Here are 5 related questions:

  1. How do you optimize a function to find maximum or minimum values?
  2. What are the steps to solve optimization problems involving constraints?
  3. How can you apply these methods to a box with a different shape or constraints?
  4. How would the solution change if the box had a top as well as a bottom?
  5. How can you check whether your solution gives a maximum or a minimum?

Tip: When solving optimization problems, always check if the second derivative is negative at the critical points to confirm a maximum.

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Math Problem Analysis

Mathematical Concepts

Optimization
Calculus
Volume of a Box
Surface Area

Formulas

Surface Area: x^2 + 4xh = 1100
Volume: V = x^2 h
Derivative: dV/dx = (1100 - 3x^2) / 4

Theorems

Optimization techniques
First derivative test
Second derivative test

Suitable Grade Level

Grades 11-12