A cone of height 9 cm with diameter of its base 18 cm is carved out from a wooden solid sphere of radius 9 cm. The percentage of the wood wasted is :  Choose the correct choice from the following.
A) 45 %
B) 56 %
C) 67 %
D) 75 %
E) none of these

Rationale: explanation : we will first subtract the cone volume from wood volume to get the wood wasted . then we can calculate its percentage . sphere volume = 4 / 3 π r 3 cone volume = 1 / 3 π r 2 h volume of wood wasted = ( 4 / 3 π ∗ 9 ∗ 9 ∗ 9 ) − ( 1 / 3 π ∗ 9 ∗ 9 ∗ 9 ) = π ∗ 9 ∗ 9 ∗ 9 cm 3 required percentage = π ∗ 9 ∗ 9 ∗ 9 / 4 / 3 π ∗ 9 ∗ 9 ∗ 9 ∗ 100 % = 3 / 4 ∗ 100 % = 75 % option d
Answer: D