Answers

  • Brainly User
2015-11-25T01:21:15+08:00
Uncut piece of cardboard:
Width: x inches
Length: 2x  inches

Piece of cardboard with four cut-out corners:
Subtract 2 × 2 inches from length and width to compute for the volume of the uncovered box formed.
Width: x - 4 inches
Length: 2x - 4 inches
Height: 2 inches
Volume: 140 cubic inches

Equation:
Length × Width × Height = Volume
(2x-4) (x-4) (2) = 140
(2x² - 8x - 4x + 16) (2) = 140
(2x² - 12x + 16) (2) = 140
4x² - 24x + 32 = 140

Quadratic equation, ax² + bc + c = 0
4x² - 24x + 32 - 140 = 0
4x² - 24x - 108 = 0

Solve by factoring:
4(x² - 6x - 27) = 0

x - 9 = 0             x + 3 = 0
x = 9                  x = -3

Choose the positive root, x = 9.

Dimensions of the uncut piece of board:
Width: x = 9 inches
Length: 2x = 2(9) = 18 inches

The dimensions are 9 inches and 18 inches.

Check:
(18 - 4) (9 - 4) (2) = 140
(14) (5) (2) = 140
140 = 140





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