Mensuration Practice question for CAT 2009

Ground work for CAT 2009 is on. Here is one simple problem.
A cone of radius r and height 3r is cut from a solid cylinder of same radius and height. A hollow hemi-sphere of diameter r is dropped into the hollow created by removing the cone in such a way that the hollow part of the sphere is facing the base of the cone. Find the volume of water that can be filled in the hollow.

For solution see : http://www.mindinsight.com/viewpotd.action?pid=4