Questions on Geometry: Geometric formulas answered by real tutors!

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Question 152917This question is from textbook College Algebra
: This problem was given by the instructor in a seperate workbook & is not in my book. I take this class via Distance Learning at UGA, so I don't really see a teacher.
"A closed rectangular box with a surface area of 28 sq. inches is to be designed. The design of the box requires that the length of the box is 2 times the width, and the depth must be 4 inches. Find the length and width of the box."
I have tried to fit this into the formula for surface area, but I just can't figure this out.This question is from textbook College Algebra
: This problem was given by the instructor in a seperate workbook & is not in my book. I take this class via Distance Learning at UGA, so I don't really see a teacher.
"A closed rectangular box with a surface area of 28 sq. inches is to be designed. The design of the box requires that the length of the box is 2 times the width, and the depth must be 4 inches. Find the length and width of the box."
I have tried to fit this into the formula for surface area, but I just can't figure this out.
Answer by scott8148(2801) About Me  (Show Source):
You can put this solution on YOUR website!
let x=width, so 2x=length

the surface area is 2[{length)(width)+(length)(depth)+(width)(depth)]

28=2[2x^2+8x+4x] __ dividing by 4 __ 7=x^2+6x __ subtracting 7 __ 0=x^2+6x-7

factoring __ 0=(x+7)(x-1)

x+7=0 __ x=-7 __ negative value not realistic

x-1=0 __ x=1 __ width=1 __ length=2