In the picture, it is a semicircle, so you have to remember to divide the area by 2. The diameter of the circle is 18, so the radius is 9. Using the formula, I'll find the area. 9²π=81π= 254.34÷2= 127.17 Now finding the radius actually help, because that semicircle's height is its radius, which is 9. 18 ×9 = 162 Now I'm going to find the shaded area. 162 - 127.17 = 34.83 mm²