Two concentric circles, the area of the small circle is (3/4) of the area of the large circle, and the area of the large circle is 12.56 square centimeters, what is the area of the ring?
两个同心圆，小圆的面积是大圆面积的(3/4)，大圆的面积是12.56平方厘米，则环形面积是多少．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">12.56 * (1/4)</gadget>
<output>3.14</output>

<result>3.14</result>