The width of a rectangular field is 20 feet less than its length. The area of the field is 12 comma 000 ft squared What is the length of the field?

Let the length be L feet, so the width is L − 20 feet. The area equation is L(L − 20) = 12,000, which gives L² − 20L − 12,000 = 0. Factoring gives (L − 120)(L + 100) = 0; the positive length is 120 feet. Therefore, the correct choice is A, 120 ft.

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