You may choose any of the triangles as they are all the same area in a rectangle. The area of the shaded triangle can be worked out as either \( \frac{1}{4}\,\,\times16.3\,\times\,12.4 = 50.53\,m^{2} ...

Remember to include the length of each side when calculating the perimeter. A compound shape is made up of several simple 2D shapes ... Add up all the sides to calculate the perimeter.