If the diameter of the small circle is a cm and the diameter of the large circle is 2a cm, what is the area of the small circle equal to the area of the large circle
小圆直径是a厘米，大圆直径是2a厘米，则小圆面积是大圆面积的多少
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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