Brainteasers keep the mind well-greased. So here's a riddle  you may like:  Drill a hole through a sphere such that the height of what remains of the sphere is 10cm . What is its remaining volume? . . . . . . . . . . . . . . . . . . . . . . . . Answer: The volume of a sphere is ( 4 / 3 )π r³ Assume any values of the sphere's radius and the hole's radius that are consistent with a 10 cm wall of the hole. So what if we assume the hole is infinitesimally small, i.e. zero?  That surely works, and the answer is simple: the volume of a 10 cm diameter sphere! Which is around 524 cm cube.  Note: I found this randomly in a magazine today and spent 5 minutes remembering the volume of sphere formula, but it was all worth it in the end. Too easy, huh?