Expressions, equations & relationships · TEKS 7.9D
Surface area
Surface area is the total area of all faces, as if you unfolded the figure into a net.
Key steps
- Rectangular prism: S = 2lw + 2lh + 2wh.
- Lateral area (sides only) = perimeter of base × height.
- Total area = lateral area + 2 × base area.
- Cube: S = 6s².
Worked example
Box 5 × 4 × 3 in. Total surface area?
- 2(5×4) + 2(5×3) + 2(4×3) = 40 + 30 + 24 = 94.
- Answer: 94 in²
Watch out: Surface area uses square units (in²). Volume uses cubic units (in³). Don’t mix them up.
Practice
5 questions with new numbers every set. Get 4 of 5 to mark this topic as practiced.