Hey there!
Let's first define what area means. Area is for two-dimensional shapes, and expressions how big something is and to what extent. There are formulas that can measure area because these shapes are totally flat, and there's nothing more to measure.
However, when we have three-dimensional figures such as rectangular prisms, we use surface area. Surface area measures the total area that the object takes up, and is a sum of the areas of all the faces. The formula for surface area of a rectangular prism is:
2(lw + wh + lh)
So if we had:
L = 5
W = 6
H = 3
We would have:
A = 2(5×6 + 6 × 3 + 5×3) =
2(30 + 18 + 15) =
2(48 + 15) =
2(63) =
A = 126 units cubed
Notice how it's units cubed because there's 3 dimensions.
Hope this helps!
