SOLUTION: This equation has me stumped. It has been a while since I have had Algebra and cant remember all the formula's. A cement walk of uniform width is built around a 20 foot by 40 fo

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Question 340288: This equation has me stumped. It has been a while since I have had Algebra and cant remember all the formula's.
A cement walk of uniform width is built around a 20 foot by 40 foot rectangle pool and the area of the walk is 700 square feet. How wide will the walk be?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
let width of walk be x feet
..
Area of pool = 40*20 = 800 sq.ft.
Length of pool + walk = 40+2x . ( x on both sides so 2x)
width of pool + walk = 20+2x
Area of pool + walk = (40+2x)(20+2x)
..
Area of pool + walk less area of pool = area of walk
(40+2x)(20+2x)-800=700
800+80x+40x+4x^2-800 =700
4x^2+120x-700=0
divide by 4
x^2+30x-175 =0
X^2+35X-5X-175=0
X(X+35)-5(X+35)=0
(X+35)(X-5)=0
X=5 or -35
iGNORE NEGATIVE VALUE.
SO X = 5 FEET THE WIDTH