The first choice is the correct answer
12 in by 22 in by 4 in
the explanation is as shown in the figure
The dimension will be x , 20 - 2x , 30 -2x
the volume= v = x(20-2x)(30-2x) = 4x³ - 100x² + 600x
differentiating with respect to x and equating to zero
dv/dx = 12x² - 200x + 600 = 0
solve for x using calculator
x = 12.7 (unacceptable) or x = 3.92 ≈ 4
∴ The dimension will be 4 , 12 , 22
12 in by 22 in by 4 in
the explanation is as shown in the figure
The dimension will be x , 20 - 2x , 30 -2x
the volume= v = x(20-2x)(30-2x) = 4x³ - 100x² + 600x
differentiating with respect to x and equating to zero
dv/dx = 12x² - 200x + 600 = 0
solve for x using calculator
x = 12.7 (unacceptable) or x = 3.92 ≈ 4
∴ The dimension will be 4 , 12 , 22