The radius of the large circle is twice the radius of the small circle, and the area of the small circle is ((())/(())) of the area of the large circle.
大圆半径是小圆半径的2倍，小圆面积是大圆面积的((())/(()))．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>