A rectangular box which i open at the top can be made from an 12-by-30-inch piece of metal by cutting a quare from each corner and bending up the ide. Find the dimenion of the box with greatet volume, where h = height, l = length, and w = width. (Note: let the width be determined by the 12-inch ide and the length by the 30-inch ide. )

Respuesta :

The dimension of the box with greatest volume is h = 2.64 in, l = 24.72 in, and w = 6.72 in.

If squares of equal sizes are to be cut out from the four corners so the four sides can be bent upwards, then the length of these squares will be the height of the box. Also twice of this length subtracted from the initial length and width of the material will be the new length and width of the box, respectively.

let x = length of square to be cut = height of the box

length of the box = 30 - 2x

width of the box = 12 - 2x

The volume of the box, which is a rectangular prism, is the product of the length, height and width.

V = l x w x h

V = (30 - 2x)(12 - 2x)(x)

V = 360x - 84x² + 4x³

To obtain the largest volume possible, the first derivative of the volume should be equal to zero.

V'(x) = 0

V = 360x - 84x² + 4x³

360 - 168x + 12x² = 0

Simplify and solve for the value of x.

360 - 168x + 12x² = 0

x² - 14x + 30 = 0

x = 7 ± √19

x₁ = 11.35

x₂ = 2.64

Check each value.

When x = 11.35 = h

l = 30 - 2x = 7.3

w = 12 - 2x = -10.7 (dimension should be positive)

When x = 2.64 = h

l = 30 - 2x = 24.72

w = 14 - 2x = 6.72

Hence, the length of square to be cut is 2.64 in.

Learn more about volume of rectangular prism here: brainly.com/question/23717073

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