The area of the base (six triangles with a base 15m and a height 7.5√3m):
[tex]A_B=6\cdot\dfrac{1}{2}\cdot15\cdot7.5\sqrt3\approx585\ m^2[/tex]
The area of side walls (six triangles with a base 15m and a height 12m)
[tex]A_W=6\cdot\dfrac{1}{2}\cdot15\cdot12=540\ m^2[/tex]
The surface area:
[tex]A_B+A_W=585+540=1,125\ m^2[/tex]
