# Thread: Surface area of a triangular prism...

1. ## Surface area of a triangular prism...

Hello everyone. I'm hoping someone can give me a little bit of help. Here's the deal, I helped a friend with her homework - calculating the surface area of triangular prisms - a couple of nights ago. It looks like I've done something wrong, however, because when she returned home she hadn't gotten a single correct answer. Anyway, here's what I've got, maybe someone can tell me if my answers are correct. This is the formula that I used: ab+ (s1+s1+s3)h

1: 144 square inches
6x8 + (10 + 6 + 8)4 = 144

2: 216 square feet

3: 48 square km

4: 60 square cm

5: 212 square yards

6: 84 square inches

2. Hello, Sherpa!

Code:
        *
/    *
*         *
|   *         *
|       *         *
a |         c *         *
|               *         *
|                   *    / h
* - - - - - - - - - - - *
b

The triangular faces are all right triangles.

. . The area of a triangle is: . $\tfrac{1}{2}ab\text{ units}^2$

. . Hence, the area of two triangles is: . $ab\text{ units}^2$

There are three rectangluar panels.
. . Their areas are: . $ah,\;bh,\;ch\text{ units}^2$

Therefore, the total surace area is: . $S \;=\; ab + (a+b+c)h$

3. It looks like the teacher has his formulas wrong! I guess I should explain that to him.