A ring x of diameter 16 inches is placed inside another ring y of diameter of 18 inches. How much fraction of the ring x surface is not covered by the ring y?
Choose one
A) 13 / 15	B) 12 / 4	C) 16 / 17	D) 22 / 16	E) 17 / 81

Rationale: the questions asks us to find the surface which is not covered by the ring x i . e . , area of the surface not covered . where as circumference is the length along the edge of the circle , 2 * pi * r implies the length of the curve pi * r ^ 2 implies area enclosed by that curve . . hence area of the circle is considered for this problem area of the ring x = pi * r ^ 2 , where r = 8 = > pi * 64 area of the ring y = pi * 81 surface not covered by the ring x = pi * 81 - pi * 64 = pi * 17 fraction of ring y ' s surface is not covered by a ring x = pi * 17 / total area of the ring y = > pi * 17 / pi * 81 17 / 81 answer e
Answer: E