Hi, when you are calculating surface area how do you combine all the formulas? I mean like how do you write them down?

Question

For example, I know all the area formulas and for surface area you have to calculate the area of each face and add them together but how do you put it down on paper?

Answer 1

Alright, so lets take a rectangular prism with square bases as an example.

You would have 2s, being the two sware bases, and 4r, being the four rectangles making up the 4 lengths of a prism. That would thus be:

2s + 4r

 

Contrast that with a rectangular prism with rectangular bases. You would have the 2 rectangles for the base themselves, the two long rectangles as two sides connecting the bases, and two thinner rectangles for the other two sides connecting the bases:

2b (bases) + 2L (length rectangles) + 2w (width rectangles)

 

One last example: square pyramid. I'll do this quick because you should be seeing the pattern here by now.

You have 4 triangles of the same size plus the base:

b + 4t

 

Hope this helps.