If the outer radius of a circle is 10 decimeters and the inner radius is 8 decimeters, what is the area of the circle in square decimeters?
一个圆的外圆半径是10分米，内圆半径是8分米，圆环的面积是多少平方分米．
<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">8 ** 2</gadget>
<output>64</output>

<gadget id="calculator">100 - 64</gadget>
<output>36</output>

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

<result>113.04</result>