Given a rectangular prism :
Height = h = 5 in
Length = l = 21 in
Width = 11 in
Lateral surface area = height * perimeter of the base = h * p
Perimeter of the base = p = 2 * ( length + width )
[tex]\begin{gathered} p=2(l+w)=2\cdot(21+11)=2\cdot32=64 \\ \end{gathered}[/tex]So, lateral area =
[tex]h\cdot p=5\cdot64=320in^2[/tex]So, the answer is : 320 in^2
