The diameter of the circle is used for the square construction, but the radius of the circle is used for the regular hexagon construction.Step-by-step explanation:
P(defective) = 3/12 = 1/4 P(good) = 1 - 1/4 = 3/4 The probability that at least 2 units are good is given by: P(2 good) + P(3 good) + P(4 good) = 0.211 + 0.422 + 0.316 = 0.949.