A cylindrical cube of radius 12 cm contains water upto a depth of 20 cm. A spherical iron ball is dropped into the tub and thus the level of water is raised by 6.75 cm. The radius of the ball is : Choose the correct choice:
A) 7 cm
B) 8.5 cm
C) 9 cm
D) 9.5 cm
E) none

Rationale: sol . let the radius of the ball be r cm . volume of ball = volume of water displaced by it . ∴ 4 / 3 ∏ r ³ = ∏ * 12 * 12 * 6.75 ⇒ r ³ = 9 * 9 * 9 ⇒ r = 9 cm . answer c
Answer: C