The circumference of the large circle is twice the circumference of the small circle, and the area of the large circle is how many times the area of the small circle.
大圆周长是小圆周长的2倍，大圆面积是小圆面积的多少倍．
<gadget id="calculator">25.12 / 3.14 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">12.56 / 3.14 / 2</gadget>
<output>2</output>

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

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

<gadget id="calculator">16 / 12.56</gadget>
<output>1.273885</output>

<gadget id="calculator">3.14 * 1.273885</gadget>
<output>3.999999</output>

<result>3.999999</result>