The area of a circle is 15 square meters. If the radius of the circle is doubled, what is the area in square meters?
一个圆的面积是15平方米，如果将这个圆的半径扩大2倍，面积应为多少平方米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<result>60</result>