To find area $ A $ use formula:

$$ A = \frac{ a^2 \sqrt{3}}{2} + 3 a l $$

After substituting $a = 8\, \text{cm}$ and $l = 10\, \text{cm}$ we have:

$$ A = \frac{ 8\, \text{cm}^2 \sqrt{3}}{2} + 3 \cdot 8\, \text{cm} \cdot 10\, \text{cm} $$$$ A = \frac{ 64\, \text{cm}^2 \sqrt{3}}{2} + 3 \cdot 80\, \text{cm}^2 $$$$ A = \frac{ 64 \sqrt{ 3 }\, \text{cm}^2}{2} + 240\, \text{cm}^2 $$$$ A = 32 \sqrt{ 3 }\, \text{cm}^2 + 240\, \text{cm}^2 $$$$ A = 295.4256\, \text{cm}^2 $$

Triangular Prism Calculator