- Find the area of one triangle using base times height divided by two. Use the right units consistently.
- Calculate the perimeter of the triangular base by adding all three side lengths together.
- Multiply the perimeter by the prism’s length (thickness or depth) to get the combined area of the rectangular faces.
- Add twice the triangle area to the product from step three for the final surface area.
| Triangle Base (cm) | Prism Length (cm) | Base Area (cm²) | Perimeter (cm) | Lateral Area (cm²) | Total Surface Area (cm²) |
|---|---|---|---|---|---|
| 5 | 10 | 12.5 | 18 | 180 | 405 |
| 8 | 15 | 24 | 30 | 450 | 498 |
| 6 | 9 | 9 | 24 | 216 | 234 |