A ring whose inner and outer diameters are 6 decimeters and 8 decimeters respectively, what is the area of the circle in square decimeters?
一个内、外圆直径分别是6分米，8分米的圆环，这个圆坏的面积是多少平方分米．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

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

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</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">50.24 - 28.26</gadget>
<output>21.98</output>

<result>21.98</result>