When considering circles there are several important facts that will assist in answering the majority of the GMAT questions related to circles. Area = πr^{2} Diameter, d = 2r Circumference = 2πr = πd Central Angle = 2(Inscribed Angle) Area of Sector = (x/360)πr^{2} Length of an Arc = (x/360) Circumference = (x/360)2πr
