Lower limit of side = 5 - 0.5 = 4.5 \\text{ cm}, area = 4.5^2 = 20.25 \\text{ cm}^2 (16 \\text{ cm}^2 to 3 significant figures). Upper limit of side = 5 + 0.5 = 5.5 \\text{ cm}, area = 5.5^2 = 30.25 \\text{ cm}^2 (36 \\text{ cm}^2 to 3 significant figures).