The volume of a square pyramid is given by:
[tex]V=\frac{1}{3}Bh[/tex]where:
B = Area of the base
h = height
so:
[tex]\begin{gathered} B=l^2 \\ where \\ l=length=30\operatorname{cm} \\ so\colon \\ B=30^2=900cm^2 \end{gathered}[/tex]Therefore:
[tex]\begin{gathered} h=45m=4500\operatorname{cm} \\ V=\frac{1}{3}(900)(4500) \\ V=1350000cm^3 \end{gathered}[/tex]