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Let w be a uniform strip width.
Then the outside (exterior) dimensions of the larger rectangle are 17+2w and 33+2w.
The area of the larger rectangle is (17+2w)*(33+2w).
The equation for the area of the border strip around the pool is
(17+2w)*(33+2w) - 17*33 = 600, or
34w + 66w + 4w^2 = 600,
4w^2 + 100w - 600 = 0 ====>
w^2 + 25w - 150 = 0,
Factor left side:
(w+30)*(w-5) = 0
The roots are w= -30 and w= 5.
Only positive root makes sense: w = 5 ft.
Answer. The strip should be 5 ft wide.
To see more similar solved problems, look into the lesson
- Problems on the area and the dimensions of a rectangle surrounded by a strip
in this site.