We are given with a regular 15-gon with a perimeter of 90 meters. In this case, side length is equal to 90/15 or 6 m. The angle inside the center is 360/15 or 24 degrees. We determine the area of each triangle (15 of them) and just multiply by 15 to get the total area. The height of each triangle is tan (12) = 3/ h where h is equal to 14.11 meters. Hence the area is 0.5*14.11*6*15 or equal to 635.13 meters.