Find the area of the circle that is 9mm
When finding an area of a circle, you need to know radius. The formula of the area of a circle is A=(pi symbol)(r squared). In this case the radius is 4.5mm because you need to divide the total by 2. Multiply 4.5mm and 4.5mm, which is the r squared. Finally multiply your answer to pi and that is the area of the circle.