What is the surface area formula of a 3-dimensional rectangle?

1 Answer
Jan 9, 2016

SA=2(wl+lh+hw)

Explanation:

For a rectangular prism with sides w,l,h, the surface area is

SA=2(wl+lh+hw)

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This occurs since there are two pairs of three different faces on every rectangular prism.

Each pair of faces is a different rectangle using two of the the three dimensions of the prism as its own side.

One side is just wl, another is just lh, and the other hw. Since there are two of each, that is reflected in the formula by the multiplication by 2.

This could also be imagined as a series of flattened-out rectangles:

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The blue rectangles are 2wl.

The yellow rectangles are 2lh.

The red rectangles are 2hw.

Again, the surface area would be

SA=2wl+2lh+2hw

=2(wl+lh+hw)