If the radius of the circle is doubled, its area will be enlarged to its original size.
圆的半径扩大到原来的2倍，它的面积就会扩大到原来的多少．
<gadget id="calculator">2 / 1</gadget>
<output>2</output>

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

<result>4</result>