If the radius of a circle is doubled, how many times is the area doubled?
一个圆的半径扩大2倍，面积扩大多少倍
<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">12.56 / 3.14</gadget>
<output>4</output>

<result>4</result>