Photorefractive keratectomy. Photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (or laser epithelial keratomileusis) (LASEK) are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses.
One acre is 43,660 square feet so 10 acres is 435,600 square feet. The area of a square is L 2 where L is the length of a side, so if the shape really is a square . L 2 = 435,600 square feet. so. L = Sqrt(435,600) = 660 feet. Penny
Total U.S farmland occupies 954 million acres. How many sq miles is this? [1 acre = 43,560 ft 2, 1 mi = 5280 ft] A) 1.16 X 10 21 mi 2 B)1.49X10 6 mi 2 C)6.11X10 11 mi 2 D)7.87X10 9 mi 2 E) none of the above 9.