volume of frustum with diameters of 30cm and 15cm and a height of 25cm

YES IT IS!!!

The volume of a frustum is gven by.....

V = (pi*h/3)(R² + Rr + r²) 

Where h is the height, R , r are the larger and smaller radii, respectively 

So.... h = 25   R = 15 and r = 7.5......so we have

V = pi*(25/3)(15² + (15)(7.5) + 7.5²) .......using the on-site calculator

$${\mathtt{\pi}}{\mathtt{\,\times\,}}\left({\frac{{\mathtt{25}}}{{\mathtt{3}}}}{\mathtt{\,\times\,}}\left({{\mathtt{15}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}\left({\mathtt{15}}{\mathtt{\,\times\,}}{\mathtt{7.5}}\right){\mathtt{\,\small\textbf+\,}}{{\mathtt{7.5}}}^{{\mathtt{2}}}\right)\right) = {\mathtt{10\,308.350\: \!894\: \!591\: \!509\: \!063\: \!7}}$$

about 10,308.35 cm³

I had to look up what  a frustum was

http://www.mathwords.com/f/frustum.htm

It's a fancy term for a  "lampshade"...........LOL!!!