SOLUTION: word problem is: the total surface area of a closed box is 350 square meters. the boxes 9 meters high and has a square base and lid. find the length of a side of the base?

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Question 809358: word problem is: the total surface area of a closed box is 350 square meters. the boxes 9 meters high and has a square base and lid. find the length of a side of the base?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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the total surface area of a closed box is 350 square meters.
the boxes 9 meters high and has a square base and lid.
find the length of a side of the base?
:
let x = one side of the square base
then
2x^2 = the area of the top and bottom of the box
and
4(9x) = the area of the 4 sides
:
Surface area equation
2x^2 + 4(9x) = 350
simplify, divide by 2
x^2 + 2(9x) = 175
A quadratic equation
x^2 + 18x - 175 = 0
Factors to
(x+25)(x-7) = 0
The positive solution
x = 7 meters, the side of the square base
:
;
Check
2(7^2) + 4(7*9) = 350