Question

A woodworker wants to build a jewelry box in the shape of a rectangular prism with a total volume of 61.3 cubic inches. The woodworker is going to use a very expensive exotic wood to build the box. He wants to choose the dimensions of the box so that the bases of the prism are squares and the box's surface area is minimized. What dimensions should he choose for the box? Round answers to 4 decimal places

Answer 1

Answer: the woodworker should choose the dimensions of the box to be approximately 3.825 inches by 3.825 inches by 1.603 inches, with a total surface area of approximately 33.512 square inches.

Explanation:

Let the side length of the square base be x, and the height of the prism be h. Then the volume of the prism is:

V = x^2h

We're given that V = 61.3 cubic inches, so:

x^2h = 61.3

We want to minimize the surface area of the box, which consists of the area of the two square bases (2x^2) plus the area of the four rectangular faces (4xh). So the total surface area is:

A = 2x^2 + 4xh

We can solve the first equation for h:

h = 61.3/x^2

Substituting this into the equation for A, we get:

A = 2x^2 + 4x(61.3/x^2)

A = 2x^2 + 245.2/x

To minimize A, we take the derivative and set it equal to zero:

dA/dx = 4x - 245.2/x^2 = 0

4x = 245.2/x^2

x^3 = 61.3

x = (61.3)^(1/3)

x ≈ 3.825

So the length of each side of the square base should be approximately 3.825 inches. We can use the equation for h to find the height:

h = 61.3/x^2

h ≈ 1.603

So the height of the prism should be approximately 1.603 inches.

Therefore, the woodworker should choose the dimensions of the box to be approximately 3.825 inches by 3.825 inches by 1.603 inches, with a total surface area of approximately 33.512 square inches.