Answer:
- rectangle: 12 ft × 24 ft
- square: 18 ft square
Step-by-step explanation:
You want the dimensions of a rectangle and square such that they have the same perimeter, but the square has an area of 36 more square feet. The rectangle is twice as long as wide.
<h3>Setup</h3>
Let x represent the side length of the square. Then its area is x², and the area of the rectangle is (x² -36).
This area is the product of length and width. The expression factors as ...
rectangle area = x² -36 = (x +6)(x -6)
<h3>Solution</h3>
If we assume these factors are the dimensions of the rectangle, then the longer dimension is twice the shorter one:
(x +6) = 2(x -6)
18 = x . . . . . . . . . add 12-x to both sides
This is the side length of the square. The rectangle dimensions are ...
x+6 = 18+6 = 24 . . . . feet long
x -6 = 18 -6 = 12 . . . . feet wide
The rectangle is 12 feet wide and 24 feet long. The square is 18 feet on a side.
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<em>Additional comment</em>
The perimeter in each case is 4x = 2((x+6) +(x -6)) = 72 ft.
The area of the rectangle is (12 ft)(24 ft) = 288 ft². The area of the square is (18 ft)² = 324 ft², a value that is 36 ft² more than the rectangle area.
<em>Alternate solution</em>
Using x for the width of the rectangle, the length is 2x and its area is x(2x) = 2x². The perimeter is 2(x +2x) = 6x, so the side length of the square is (6x)/4 = 3/2x and its area is (3/2x)² = 9/4x².
The difference is 36 square feet, so we have ...
9/4x² -2x² = 36 = x²/4 ⇒ x = √(36·4) = 6·2 = 12 . . . . width of rectangle
