Area, SM-Bank 155 A semi-circle has an area of 470 square centimetres. Calculate the diameter of the semi-circle, giving your answer to 1 decimal place. (2 marks) --- 4 WORK AREA LINES (style=lined) --- Show Answers Only \(34.6\ \text{cm}\) Show Worked Solution \(\text{Area of full circle}\ =2 \times 470 = 940\ \text{cm}^{2}\) \(A\) \(=\pi r^{2} \) \(940\) \(= \pi r^2\) \(r^{2}\) \(= \dfrac{940}{\pi} \) \(r\) \(=\sqrt{299.211…}\) \(=17.30\ \text{cm}\) \(\therefore\ \text{Diameter}\ = 2 \times 17.30 = 34.6\ \text{cm (1 d.p.)}\)