Given that the diameter of the circle is 30 meters, find the area of the circle in square meters.
已知圆的直径是30米，求圆的面积是多少平方米．
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 ** 2</gadget>
<output>225</output>

<gadget id="calculator">3.14 * 225</gadget>
<output>706.5</output>

<result>706.5</result>