Two circular blocks are placed one above the other. Block A at the bottom has a diameter of 24 cm. Block B at the top has a diameter of 16 cm. What fraction of Block A's surface is not covered by Block B? Choose the correct choice from the following answers:	A) 5/6	B) 2/3	C) 2/9	D) 18/20	E) 4/5
The questions asks us to find the surface which is not covered by the Block B 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 Block B=pi* r^2, where r=8   =&gt;pi*64   Area of the Block A=pi*144   Surface not covered by the Block B=pi*144-pi*64=Pi*80   fraction of Block A surface is not covered by a Block B= Pi*80/total area of the Block A   =&gt;Pi*80/Pi*144=2/9   Answer 2/9
<result>C</result>
Two circular blocks are placed one above the other. Block A at the bottom has a diameter of 24 cm. Block B at the top has a diameter of 16 cm. What fraction of Block A's surface is not covered by Block B?