We have to calculate the perimeter of the figure to the nearest tenth of a millimeter. This figure is made of a rectangle and a half of a circle. The first figure has the perimeter: 3 + 6 + 3 = 12 mm. The second figure has the perimeter: 2 * Pi * r / 2 = Pi * r ; and the radius : r = 6/2 = 3 mm. So Pi * 3 = 3.14 * 3 = 9.42. Fimally : 12 + 9.42 = 21.42 or 21.4 to the nearest tenth. Answer: C. 21.4 millimeters.
