The outer diameter of a ring is 12 cm, the inner diameter is 6 cm, what is the area of the ring in cm**2.
一个环形外圆直径是12厘米，内圆直径是6厘米，环形面积是多少cm**2．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">3.14 * 36</gadget>
<output>113.04</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<gadget id="calculator">113.04 - 28.26</gadget>
<output>84.78</output>

<result>84.78</result>