51.
									
										A cylindrical tub of radius 12cm contains water upto a depth of 20 cm. A spherical iron ball is dropped in to the tub and thus the level of water is raised by 6.75cm/ The radius of the ball is : 
									
								
															
														
																									
										A:
											4.5 cm
									
																										
										B:
											6cm
									
																										
										C:
											9cm
									
																										
										D:
											7.25 cm
									
																								 
							
																
									The answer is:
										C