A ball's volume and area are


1/2 the area of a box is 3 sides.
Area is 3d^{2}, or 12r^{2}.
Volume is 1/2 d^{3}, or 4r^{3}.
details.... 
The volume of a box is V_{cube} = d^{3}. The volume of a ball is V_{sphere} = 4/3 pi r^{3} = pi/6 d^{3}. An approximation of 3/6 for pi/6 is 4.5% low. The area of a box is A_{cube} = 6d^{2}. 
So unless you care about the 5%, please don't tell children to use 4/3 pi r^{3}...
The amusement of finding pi in an equation noone remembers is somewhat limited.
Comments encouraged.  Mitchell N Charity <mcharity@lcs.mit.edu>) 