Question 120235
You have two solid figures whose volume adds up to {{{2600ft^3}}}


let the height of the cylinder part be h, then the height of the conical part is h/3.


The volume of the cylinder is {{{V[cyl]=pi*r^2*h}}}, and the volume of the conical part, in terms of the height of the cylinder is {{{V[cone]=(1/3)*pi*r^2*(h/3)}}}


Add these two volumes together {{{V=(pi*9^2*h)+((1/3)*pi*9^2(h/3))=2600ft^3}}}


Simplify:


{{{(pi*9^2*h)+(pi*9^2(h/9))=2600ft^3}}}


{{{(pi*9^2)(h+(h/9))=2600ft^3}}}


{{{(pi*9^2)(10h/9)=2600ft^3}}}


{{{(pi*9)(10h)=2600ft^3}}}


{{{h=((2600)/(90*pi))ft}}}


{{{h=((260)/(9*pi))ft}}} which is the height of the cylinder part.


To that we have to add the height of the conical part, {{{h/3=(((260)/(9*pi))/3)ft=((260)/(27*pi))ft}}}


So the total height is {{{h[t]=((260)/(9*pi))+((260)/(27*pi))ft=(780/(27*pi))+(260/(27*pi))=1040/(27*pi)}}}.


A little calculator work shows this to be approximately 12.26.  Your question requires rounding to one decimal place, so you want 12.3 -- however, it is really inappropriate to express this answer to the nearest 10th, since the given volume was expressed only to the nearest whole cubic foot. 12.3 feet would be correct IF the volume had been given as 2600.0 cubic feet.  You should never express an answer with greater precision than the least precise of your given measurements.


Hope this helps,
John