SOLUTION: a cement walk of uniform width is built around a 20 foot by 40 foot rectangular pool an the area of the walk is 700 square feet. How wide will the walk be?

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Question 269619: a cement walk of uniform width is built around a 20 foot by 40 foot rectangular pool an the area of the walk is 700 square feet. How wide will the walk be?
Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
The pool covers 800 square feet.
The new cement walk plus pool will have dimensions
(i) %2820%2B2x%29%2840%2B2x%29
the area of the walkway - area of pool = 700, or
(ii) %2820%2B2x%29%2840%2B2x%29+-+800+=+700
distributing the left we get
(iii) 800+%2B+120x+%2B+4x%5E2+-+800+=+700
simplify the left to get
(iv) 4x%5E2+%2B+120x+=+700
subtract 700 and set = 0 to get
(v) 4x%5E2+%2B+120x+-+700+=+0
solving for x by the quadratic, we get
x = -35 or x = 5.
SInce we can use x = -35, we have
x = 5
walkway = 5 feet wide