Answer:
(d) 25 feet and 20 feet
Explanation:
You want the possible dimensions of a pool with an area of 500 square feet and a perimeter of 90 feet.
Area
The area is the product of the length and width. The area of the pools offered in the answer choices are ...
(a) 15·30 = 450 . . . square feet
(b) 10·35 = 350 . . . square feet
(c) 50·10 = 500 . . . square feet
(d) 25·20 = 500 . . . square feet
The area requirement eliminates answer choices A and B.
Perimeter
The perimeter is twice the sum of length and width. The perimeters of the possible pools are ...
(c) 2(50 +10) = 120 . . . feet
(d) 2(25 +20) = 90 . . . feet
The perimeter requirement eliminates answer choice C.
The pool's possible length and width are 25 feet and 20 feet, choice D.
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Additional comment
You could write a quadratic equation for the pool dimensions, but doing that will generally involve more work than checking the given answer choices.
If x is the width, then 45-x is the length, and the area is ...
x(45 -x) = 500
x² -45x +506.25 = -500 +506.25 . . . multiply by -1, complete the square
x = 22.5 -√6.25 = 20 . . . . take the square root; width is the smaller dimension
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