SOLUTION:
There are 2 errors here.
1.The height used in finding the volume is the perpendicular height, not the slant height
2. The multiplication was wrong.
CORRECT SOLUTION
[tex]V=\frac{1}{2}Bh[/tex][tex]B=20\times20=400ft^2[/tex]
Using pythagoras theorem, we find h to be;
[tex]\begin{gathered} h=\sqrt{26^2-10^2} \\ h=24cm \end{gathered}[/tex][tex]V=\frac{1}{3}\times400\times24=3200ft^3[/tex]
