Question 150913
See http://math.about.com/od/formulas/ss/surfaceareavol_2.htm

{{{V = pi*r^2*h/3}}}

Area of the base is {{{pi *r^2}}}
{{{500 = 20 * h/3}}}
{{{1500/20 = h }}}
{{{75 = h}}}  inches