If a drawing has an outer circle of diameter 30 and an inner circle of diameter 24, then what fraction of outer circle's surface is not covered by the inner circle?  Select the correct option.
A) 3 / 6	B) 8 / 24	C) 14 / 16	D) 9 / 25	E) 2 / 3

Rationale: the questions asks us to find the surface which is not covered by the inner circle 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 inner circle = pi * r ^ 2 , where r = 12 = > pi * 144 area of the outer circle = pi * 225 surface not covered by the inner circle = pi * 225 - pi * 144 = pi * 81 fraction of outer circle ' s surface is not covered by the inner circle = pi * 81 / total area of the outer circle = > pi * 81 / pi * 225 = 9 / 25 answer is d
Answer: D