How to calculate surface area of rectangular hollow section?

Question

How to calculate surface area of rectangular hollow section?

Answer 1

length*width

sorry I did not understand. A 3D rectangle is called a cubiod.

Answer 2

The cross-sectional dimensions are width and height and then there is the overall length.  For the external surface area, you would have two areas that are the product of the width and length and you would have two areas that are the product of the height and length.  So, the total external surface area would like:

Surface area = 2*(width * length) + 2*(height * length)

Surface area = 2*length*(width + height)  

Answer 3

Let:

L = outside length of the rectangular section

W = outside width of the section

H = outside depth of the section

t = thickness of the walls of the section

S = Total surface area of the section

Assuming that the section is not closed at the ends:

S = 2(WL) + 2(HL) + 2(W-2t)L + 2(H -2t)L

If the section is closed at the ends then the total surface area is:

S = 2(WL) + 2(WH) + "(W-2t)(L-2t) + 2(H-2t)(L - 2t) + 2WH

+ 2(W-2t)(h-2t)