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 the most appropriate option
A) 13/15	B) 12/4	C) 16/17	D) 22/16	E) 17/81
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   =&gt;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   =&gt;Pi*17/Pi*81   17/81   Answer 17/81
<result>E</result>
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?