Question 897721
The radius is half the diameter, so r=15 feet.


Let h = tallness of only the straight cylinder portion.  The whole silo tallness will be {{{highlight_green(h+r)}}}.  Your question is unclear, but you want a final result of either h or h+r.


Volume of the silo, {{{h*pi*r^2+(1/2)(4/3)pi*r^3=11925pi}}}.
{{{h*pi*r^2+(2/3)pi*r^3=11925pi}}}
{{{h*r^2+(2/3)r^3=11925}}}
{{{hr^2=11925-(2/3)r^3}}}
{{{h=11925/r^2-(2/3)(r^3)/r^2}}}
{{{h=11925/225-(2/3)r}}}
{{{h=11925/225-2*15/3}}}
{{{h=11925/225-10=53-10}}}
{{{highlight(h=43)}}} feet, just the straight cylinder part.


The whole silo from top to bottom is {{{43+15=58}}} feet.