Perimeter of semi-circular field

Area = $\frac{1}{2}\pi r^2 = 15400 \implies \frac{1}{2} \times \frac{22}{7} \times r^2 = 15400 \implies r^2 = 9800 \implies r = 70\sqrt{2}\text{ m}$. Perimeter of semicircle = $\pi r + 2r = r(\pi + 2) = 70\sqrt{2} \left(\frac{22}{7} + 2\right) = 70\sqrt{2} \times \frac{36}{7} = 360\sqrt{2}\text{ m}$.