Check the picture below.
[tex]\textit{volume of a pyramid}\\\\ V=\cfrac{Bh}{3} ~~ \begin{cases} B=\stackrel{base's}{area}\\ h=height\\[-0.5em] \hrulefill\\ B=\stackrel{18\times 18}{324}\\ h=18 \end{cases}\implies V=\cfrac{(324)(18)}{3}\implies V=1944~cm^3[/tex]
